Modified parser to handle alt type andadded a few tests

ast.ml - modified arm types for easier polymorphism
       - fixed a bug in fmt_type_arm
dead.ml - modified arm types for easier polymorphism
common.ml - added 'either'
          - added some useful auxiliary functions
item.ml - modified arm code to be more polymorphic and handle both alt-tag and alt-type, also fixed the problematic case in bad-alt.rs
Makefile - added XFAIL for new alt-type test
bad-alt.rs - added test for invalid alt syntax
alt-type-simple.rs - added simple test for alt type

1 files changed, 6 insertions, 0 deletions

diff --git a/src/test/compile-fail/bad-alt.rs b/src/test/compile-fail/bad-alt.rs
new file mode 100644
index 00000000..f2582879
--- /dev/null
+++ b/src/test/compile-fail/bad-alt.rs
@@ -0,0 +1,6 @@
+// error-pattern: Unexpected token 'x'
+
+fn main() {
+  let int x = 5;
+  alt x;
+}