GLM 0.9.7.1

Improvements:

• Improved constexpr for constant functions coverage #198
• Added to_string for quat and dual_quat in GTX_string_cast #375
• Improved overall execution time of unit tests #396

Fixes:

• Fixed strict alignment warnings #235 #370
• Fixed link errors on compilers not supported default function #377
• Fixed compilation warnings in vec4
• Fixed non-identity quaternions for equal vectors #234
• Fixed excessive GTX_fast_trigonometry execution time #396
• Fixed Visual Studio 2015 'hides class member' warnings #394
• Fixed builtin bitscan never being used #392
• Removed unused func_noise.* files #398