Multiple audio stream playback, volume control, pausing

* Fix Speaking state, use latest voice API version

* Speaking state would remain stuck on after playing particularly long
stretches of audio. So far as I can tell, playing 5 frames of silence
BEFORE changing the state seems to do the trick.
* Added new constant to make sure the library uses v3 of the voice api,
which it is written for.
* Heartbeat interval adjusted by * .75 as recommended by Discord.

* Initial version of new Audio wrapper.

* Single audio file case, as before..

* Loop over all available audio samples.

* Combine audio streams, account for volume.

* Cheaper explicit Opus silence frames.

As per Discord's recommendation, use a well-known 3-byte silence frame when needed.

* A bit of cleanup

Cleanup some of the code, rename some short-form fields to longer forms
(e.g. `s/src/source`), and remove a breaking change.

`Handler::play` was changed to return `LockedAudio` instead of `()`. If
someone were to rely on `Handler::play` returning `()`, the return type
change would break their code. Instead, this functionality has been
added to a new `Handler::play_returning` function.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/voice/mod.rs b/src/voice/mod.rs
index 70f1ae2..cae84a7 100644
--- a/src/voice/mod.rs
+++ b/src/voice/mod.rs
@@ -11,7 +11,7 @@ mod payload;
 mod streamer;
 mod threading;
 
-pub use self::audio::{AudioReceiver, AudioSource, AudioType};
+pub use self::audio::{Audio, AudioReceiver, AudioSource, AudioType, LockedAudio};
 pub use self::dca::DcaMetadata;
 pub use self::error::{DcaError, VoiceError};
 pub use self::handler::Handler;
@@ -26,5 +26,6 @@ pub(crate) enum Status {
     Connect(ConnectionInfo),
     #[allow(dead_code)] Disconnect,
     SetReceiver(Option<Box<AudioReceiver>>),
-    SetSender(Option<Box<AudioSource>>),
+    SetSender(Option<LockedAudio>),
+    AddSender(LockedAudio),
 }