Miscellaneous code cleanup in audio framework

Changes:
 - Move declaration of kClassPathName to top of file so it can be used
   in more than one place, instead of "android/media/AudioSystem".
 - Make private methods static.
 - Add comment to stream_type, audio_mode, force_use types that they must match
   values in AudioSystem.java.
 - Add comment about unused types mp3_sub_format and vorbis_sub_format.
 - Fix typos.
 - Use @ in javadoc comments.
 - Delete dead APIs setMode, getMode, setRouting, getRouting in AudioSystem.java
   (they are all hidden, deprecated, and unused by rest of framework)
 - Delete unused private log method.
 - Fix pathname for android_media_AudioSystem.cpp.
 - Improve code formatting for space after == and !=.
 - Add logging of delta for changing audio policy manager ref count.

Change-Id: I18037c7beb8ab76d1fda08c11e589f6e591d36e1