Miniaudio

- Fix some warnings when compiling with Visual C++.

- Fix errors with channel mixing when increasing the channel count.
- Improvements to the build system for the OpenAL backend.
- Documentation fixes.

- API CHANGE: The mal_context_init() function now takes a pointer to a mal_context_config object for
configuring the context. The works in the same kind of way as the device config. The rationale for this
change is to give applications better control over context-level properties, add support for backend-
specific configurations, and support extensibility without breaking the API.
- API CHANGE: The alsa.preferPlugHW device config variable has been removed since it's not really useful for
anything anymore.
- ALSA: By default, device enumeration will now only enumerate over unique card/device pairs. Applications
can enable verbose device enumeration by setting the alsa.useVerboseDeviceEnumeration context config
variable.
- ALSA: When opening a device in shared mode (the default), the dmix/dsnoop plugin will be prioritized. If
this fails it will fall back to the hw plugin. With this change the preferExclusiveMode config is now
honored. Note that this does not happen when alsa.useVerboseDeviceEnumeration is set to true (see above)
which is by design.
- ALSA: Add support for excluding the "null" device using the alsa.excludeNullDevice context config variable.
- ALSA: Fix a bug with channel mapping which causes an assertion to fail.
- Fix errors with enumeration when pInfo is set to NULL.
- OSS: Fix a bug when starting a device when the client sends 0 samples for the initial buffer fill.

- API CHANGE: The log callback is now per-context rather than per-device and as is thus now passed to
mal_context_init(). The rationale for this change is that it allows applications to capture diagnostic
messages at the context level. Previously this was only available at the device level.
- API CHANGE: The device config passed to mal_device_init() is now const.
- Added support for OSS which enables support on BSD platforms.
- Added support for WinMM (waveOut/waveIn).
- Added support for UWP (Universal Windows Platform) applications. Currently C++ only.
- Added support for exclusive mode for selected backends. Currently supported on WASAPI.
- POSIX builds no longer require explicit linking to libpthread (-lpthread).
- ALSA: Explicit linking to libasound (-lasound) is no longer required.
- ALSA: Latency improvements.
- ALSA: Use MMAP mode where available. This can be disabled with the alsa.noMMap config.
- ALSA: Use "hw" devices instead of "plughw" devices by default. This can be disabled with the
alsa.preferPlugHW config.
- WASAPI is now the highest priority backend on Windows platforms.
- Fixed an error with sample rate conversion which was causing crackling when capturing.
- Improved error handling.
- Improved compiler support.
- Miscellaneous bug fixes.

- API CHANGE: Introduced the notion of a context. The context is the highest level object and is required for
enumerating and creating devices. Now, applications must first create a context, and then use that to
enumerate and create devices. The reason for this change is to ensure device enumeration and creation is
tied to the same backend. In addition, some backends are better suited to this design.
- API CHANGE: Removed the rewinding APIs because they're too inconsistent across the different backends, hard
to test and maintain, and just generally unreliable.
- Added helper APIs for initializing mal_device_config objects.
- Null Backend: Fixed a crash when recording.
- Fixed build for UWP.
- Added support for f32 formats to the OpenSL|ES backend.
- Added initial implementation of the WASAPI backend.
- Added initial implementation of the OpenAL backend.
- Added support for low quality linear sample rate conversion.
- Added early support for basic channel mapping.

- API CHANGE: Add user data pointer as the last parameter to mal_device_init(). The rationale for this
change is to ensure the logging callback has access to the user data during initialization.
- API CHANGE: Have device configuration properties be passed to mal_device_init() via a structure. Rationale:
1) The number of parameters is just getting too much.
2) It makes it a bit easier to add new configuration properties in the future. In particular, there's a
chance there will be support added for backend-specific properties.
- Dropped support for f64, A-law and Mu-law formats since they just aren't common enough to justify the
added maintenance cost.
- DirectSound: Increased the default buffer size for capture devices.
- Added initial implementation of the OpenSL|ES backend.