The first of probably many commits adding additional SIMD functionality to GLM.

This commit places simdVec4::Data into a nameless union with x, y, z, w components. This will allow .x, etc syntax to be used in the same way as standard vec4/3/2. This requires a warning silencer for MSVC. No preprocessor options controlling this behaviour yet, but will probably come.

Also added is operator[] for simdVec4 which is the same as vec4's.

Finally, the simd_vec4 test program has been updated with basic tests. This will continue to be updated as modifications are made.
Added initializers to simdVec4 and simdMat4 default constructors. This keeps them consistent with the vec4/mat4 counterparts. This can be disabled by #defining GLM_SIMD_NO_DEFAULT_INIT before including the header files.

Added missing implementations of binary and unary constant operators for simdMat4.

The simd_mat4 test program has been updated with consistency tests to check for consistency between mat4 and simdMat4. The m / m test fails at the moment. As far as I can tell, it's due to a difference between glm::mat4::_inverse() and glm::inverse(). Needs more investigation.

Const-corrected a couple of matrix intrinsic functions.

Added a constructor to simdMat4 which takes a __m128[4].
Added GLM_SIMD_NO_TYPE_UNION preprocessor option for controlling whether or not a nameless union should be used to allow x, y, z and w access.
More const-correctness in matrix intrinsic functions.
Added GLM_ARCH_SSE4
simdVec4::dot() will now use SSE4's _mm_dp_ps intrinsic (dpps instruction) where available. I was able to see a performance difference in only a few contrived tests, so further testing here may be needed. This may well be due to the tests themselves being dodgy.
Fixed some MinGW/GCC warnings.
Fixed MinGW-W64 SSE compilation errors where conflicts would occur when intrin.h was included after setup.hpp. Fixed this by just explicitly including intrin.h in setup.hpp for MinGW builds. Untested with non-w64 MinGW.

Fixed a GCC warning in quaternion.

Fixed a GCC compilation error in fvec4SIMD::operator[].
Merge git://github.com/mackron/glm.git
Fixed space characters
Fixed merge