add defines for sound functions
SOUND_VOLUME, SOUND_BALANCE, SOUND_CHANNELS, SOUND_STEREO_WIDTH ...
defines depend on target
require "sound_defines" to add them to rb.sound_settings[]
consolidates:
sound_set, sound_current, sound_default, sound_min, sound_max,
sound_unit, sound_pitch, sound_val2phys to a single function
rb.sound("name", setting, [value])
require "sound.lua" for old functionality
Change-Id: Ice695218aa433f4fcbb48fbd6b8a9bf29c994110
