[MIPS] WebRTC optimizations for MIPS

For Little-endian only

This is Patch Set 3, committed to git on Jan 22 2013:
Optimizations for MIPS32Rev1 added.
Check for various MIPS architecture configurations added. Preprocessor flags modified accordingly.

Aosp Change-Id: I67f64ae4ef3311baad4223a7d2e6118bff8e84da

Change-Id: I6530933640ef7210974bb869abda12480e491012