GLM_GTX_noise: Procedural noise functions

Defines 2D, 3D and 4D procedural noise functions Based on the work of Stefan Gustavson and Ashima Arts on "webgl-noise": https://github.com/ashima/webgl-noise Following Stefan Gustavson's paper "Simplex noise demystified": http://www.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf Defines the half-precision floating-point type, along with various typedefs for vectors and matrices.

<glm/gtx/noise.hpp> need to be included to use these functionalities.