Add support for OpenSSL 1.1.0

This commit is relatively major refactoring of the `openssl-sys` crate as well
as the `openssl` crate itself. The end goal here was to support OpenSSL 1.1.0,
and lots of other various tweaks happened along the way. The major new features
are:

* OpenSSL 1.1.0 is supported
* OpenSSL 0.9.8 is no longer supported (aka all OSX users by default)
* All FFI bindings are verified with the `ctest` crate (same way as the `libc`
  crate)
* CI matrixes are vastly expanded to include 32/64 of all platforms, more
  OpenSSL version coverage, as well as ARM coverage on Linux
* The `c_helpers` module is completely removed along with the `gcc` dependency.
* The `openssl-sys` build script was completely rewritten
  * Now uses `OPENSSL_DIR` to find the installation, not include/lib env vars.
  * Better error messages for mismatched versions.
  * Better error messages for failing to find OpenSSL on a platform (more can be
    done here)
  * Probing of OpenSSL build-time configuration to inform the API of the `*-sys`
    crate.
* Many Cargo features have been removed as they're now enabled by default.

As this is a breaking change to both the `openssl` and `openssl-sys` crates this
will necessitate a major version bump of both. There's still a few more API
questions remaining but let's hash that out on a PR!

Closes #452

1 files changed, 55 insertions, 53 deletions

diff --git a/README.md b/README.md
index d919cff1..54f208b4 100644
--- a/README.md
+++ b/README.md
@@ -6,13 +6,16 @@
 
 ## Building
 
-rust-openssl depends on both the OpenSSL runtime libraries and headers.
+rust-openssl depends on the OpenSSL runtime libraries version 1.0.1 or above.
+Currently the libraries need to be present in the build environment before this
+crate is compiled, and some instructions of how to do this are in the sections
+below.
 
 ### Linux
 
-On Linux, you can install OpenSSL via your package manager. The headers are
-sometimes provided in a separate package than the runtime libraries - look for
-something like `openssl-devel` or `libssl-dev`.
+On Linux, you can typically install OpenSSL via your package manager. The
+headers are sometimes provided in a separate package than the runtime libraries
+- look for something like `openssl-devel` or `libssl-dev`.
 
 ```bash
 # On Ubuntu
@@ -23,79 +26,78 @@ sudo pacman -S openssl
 sudo dnf install openssl-devel
 ```
 
+If installation via a package manager is not possible, or if you're cross
+compiling to a separate target, you'll typically need to compile OpenSSL from
+source. That can normally be done with:
+
+```
+curl -O https://www.openssl.org/source/openssl-1.1.0b.tar.gz
+tar xf openssl-1.1.0b.tar.gz
+cd openssl-1.1.0b
+export CC=...
+./Configure --prefix=... linux-x86_64 -fPIC
+make -j$(nproc)
+make install
+```
+
 ### OSX
 
-OpenSSL 0.9.8 is preinstalled on OSX. Some features are only available when
-linking against OpenSSL 1.0.0 or greater; see below on how to point
-rust-openssl to a separate installation. OSX releases starting at 10.11, "El
-Capitan", no longer include OpenSSL headers which will prevent the `openssl`
-crate from compiling.
+Although OpenSSL 0.9.8 is preinstalled on OSX this library is being phased out
+of OSX and this crate also does not support this version of OpenSSL. To use this
+crate on OSX you'll need to install OpenSSL via some alternate means, typically
+homebrew:
 
-For OSX 10.11 you can use brew to install OpenSSL and then set the environment variables
-as described below.
 ```bash
 brew install openssl
-export OPENSSL_INCLUDE_DIR=`brew --prefix openssl`/include
-export OPENSSL_LIB_DIR=`brew --prefix openssl`/lib
 ```
 
-May be necessary clean the repository with `cargo clean` before build again.
+### Windows MSVC
 
-### Windows
+On MSVC it's unfortunately not always a trivial process acquiring OpenSSL.
+Perhaps the easiest way to do this right now is to download [precompiled
+binaries] and install them on your system. Currently it's recommended to
+install the 1.1.0b light installation if you're choosing this route.
 
-On Windows, consider building with [mingw-w64](http://mingw-w64.org/).
-Build script will try to find mingw in `PATH` environment variable to provide
-Cargo with location where openssl libs from mingw-w64 package may be found.
+[precompiled binaries]: http://slproweb.com/products/Win32OpenSSL.html
 
-mingw-w64 can be easily installed by using [MSYS2](http://msys2.github.io/). Install MSYS2 according to the instructions, and then, from an MSYS2 Shell, install mingw-w64:
+Once a precompiled binary is installed you can configure this crate to find the
+installation via an environment variable:
 
-32-bit:
-```bash
-pacman -S mingw-w64-i686-gcc
-``` 
-
-64-bit
-```bash
-pacman -S mingw-w64-x86_64-gcc
+```
+set OPENSSL_DIR=C:\OpenSSL-Win64
 ```
 
-and then install the mingw-w64 toolchain.
+After that, you're just a `cargo build` away!
 
-32-bit:
-```bash
-pacman -S mingw-w64-i686-toolchain
-```
+### Windows GNU (MinGW)
 
-64-bit:
-```bash
-pacman -S mingw-w64-x86_64-toolchain
-```
+The easiest way to acquire OpenSSL when working with MinGW is to ensure you're
+using [MSYS2](http://msys2.github.io) and to then execute:
 
-Alternatively, install OpenSSL from [here][1]. Cargo will not be able to find OpenSSL if it's
-installed to the default location. You can either copy the `include/openssl`
-directory, `libssl32.dll`, and `libeay32.dll` to locations that Cargo can find
-or pass the location to Cargo via environment variables:
+```
+# 32-bit
+pacman -S mingw-w64-i686-openssl
 
-```bash
-env OPENSSL_LIB_DIR=C:/OpenSSL-Win64 OPENSSL_INCLUDE_DIR=C:/OpenSSL-Win64/include cargo build
+# 64-bit
+pacman -S mingw-w64-x86_64-openssl
 ```
 
+And after that, a `cargo build` should be all you need!
+
 ### Manual configuration
 
 rust-openssl's build script will by default attempt to locate OpenSSL via
-pkg-config. This will not work in some situations, for example, on systems that
-don't have pkg-config, when cross compiling, or when using a copy of OpenSSL
+pkg-config or other system-specific mechanisms. This will not work in some
+situations however, for example cross compiling or when using a copy of OpenSSL
 other than the normal system install.
 
 The build script can be configured via environment variables:
-* `OPENSSL_LIB_DIR` - If specified, a directory that will be used to find
-    OpenSSL runtime libraries.
-* `OPENSSL_INCLUDE_DIR` - If specified, a directory that will be used to find
-    OpenSSL headers.
-* `OPENSSL_STATIC` - If specified, OpenSSL libraries will be statically rather
-    than dynamically linked.
 
-If either `OPENSSL_LIB_DIR` or `OPENSSL_INCLUDE_DIR` are specified, then the
-build script will skip the pkg-config step.
+* `OPENSSL_DIR` - If specified, a directory that will be used to find
+  OpenSSL installation. It's expected that under this directory the `include`
+  folder has header files and a `lib` folder has the runtime libraries.
+* `OPENSSL_STATIC` - If specified, OpenSSL libraries will be statically rather
+  than dynamically linked.
 
-[1]: http://slproweb.com/products/Win32OpenSSL.html
+If `OPENSSL_DIR` is specified, then the build script will skip the pkg-config
+step.