Cmake build option to enable / disable SIMD.
Cmake build option to enable / disable SIMD.

Added cmake build option to enable / disable SIMD support.  SIMD support is
enabled by default.

For example, to build with SIMD support disabled on Linux run...

cmake -Dmathfu_enable_simd=0 -G'Unix Makefiles'
make

Tested:
Verified the project builds with SIMD support disabled.

Bug: 16626436
Change-Id: Id141afe281ce0865e609959f33004daf5438c29e

google/mathfu,google/mathfu,google/mathfu