Add MIPS64r6 support for libpixelflinger

Added ARMtoMips64Assembler class that translates ARM instructions to MIPS64r6
instructions.
Added MIPS64r6 assembly implementations for col32cb16_blend and t32cb16_blend
functions.
Added MIPS32r2 assembly implementation for col32cb16_blend function.
Added tests for MIPS64r6 (assembler, disassembler and assembly implementation
functions).
Added MIPS32 tests for assembly implementation functions.
Minor bug fixes for MIPS32r2 branch.

Change-Id: I69e49622117be5b8167628e9702db6aafb1849d7