VAD refactoring: Code style changes of local function.
VAD refactoring: Code style changes of local function.

Changes applied to local GmmProbability():
* Replaced shift macros with shift operations
* Indentation and braces
* Removed redundant code
* Removed unnecessary type casts
* Name changes
* Adjusted comments

Tested with vad_unittests and audioproc_unittest

BUG=None
TEST=None

Review URL: https://webrtc-codereview.appspot.com/475002

git-svn-id: 917f5d3ca488f358c4d40eaec14422cf392ccec9@1991 4adac7df-926f-26a2-2b94-8c16560cd09d

TimothyGu/libilbc,ShiftMediaProject/libilbc,mwgoldsmith/ilbc,TimothyGu/libilbc,TimothyGu/libilbc,mwgoldsmith/ilbc,mwgoldsmith/libilbc,mwgoldsmith/ilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,mwgoldsmith/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,mwgoldsmith/libilbc,ShiftMediaProject/libilbc,mwgoldsmith/libilbc,mwgoldsmith/ilbc