Add defined(MA_APPLE_MOBILE) guard around AVAudioSessionCategory code

Public issue #101

  * The session category can now be configured via the context config. When
    set to ma_ios_session_category_default, it will try PlayAndRecord,
    Playback and Record (in that order) until one works. If none work it
    leave the category untouched. This will also set the DefaultToSpeaker
    option since in most cases an application will want audio to be emitted
    from the speaker rather than the receiver.  If the application does not
    want to change the session category, use ma_ios_session_category_none.

  * The session category options can now be configured via the context
    config. This maps to the AVAudioSessionCategoryOption flags.

Public issues #101, #113

Public issue #108

Public issue #110

Public issue #110

Public issue #110

Public issue #114.

This will be replaced with a more complete solution later.

Public issue #105.

These compilation errors are a result of the recent change to dr_wav to
add support for allocation callbacks.

remove a stray garbage byte (0x10) from the source file which makes visual studio unable to open it sometimes :o

remove a stray garbage byte (0x10) from the source file which makes visual studio unable to open it sometimes :o

This change enabled the use of low-latency shared mode if the desired
sample rate matches the native sample rate.

AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM is incompatible in exclusive mode
and low-latency shared mode.