Adding 2f for neon.

The main benefit of this is to store compact 2D vectors which neon supports.

Tested:
Ran Unittests with gmath::Vector<T,2> class which now uses this.

Change-Id: I1f04c9ad4db7d3f1a7a55849551421615ffd7503
Rewrite dot, cross and store for vec3 to improve performance

Tested:
Ran Vector Unittests from gmath related to dot, cross, normalize, and store
On Arm this improves performance by about 20%
On x86 this improves performance by about 30%

Change-Id: I0218b99ff938aade715324311427bf84db65d4f2
Return the determinant from simd4x4_inverse.

Returning the determinant from simd4x4_inverse() allows the caller to
optionally test whether the matrix supplied is invertible.

Bug: 17163723
Change-Id: Id4f048a7faa1a47da91ca9b24fa264abf421f66e
Fixed variable narrowing conversion warning when compiling with GCC.

Tested:
Verified dependent project compiles successfully using gcc and -Wall
for NEON platforms (Android).

Bug: 17007481
Change-Id: Ifeb7e33c1868c684f9e29005a4a31940f79bb034
Modified simd4f to support for SSE1/2.

Conditionally compiled simd4f_dot3_splat() to use a SSE1/2
implementation.

Tested:
Verified all unit tests of a dependent project pass.
Bug: 17007481

Change-Id: I457c1cf2cf3eb9aa1555e5b40884f6310abdf33b