Updated glm platform detect from upstream 0.9.9-a2
Updated glm platform detect from upstream 0.9.9-a2

Cherry picked from commit dd48b56e44d699a022c69155c8672caacafd9e8a
to permit building with gcc version 7.3
https://github.com/g-truc/glm/commit/dd48b56e44d699a022c69155c8672caacafd9e8a

patriciogonzalezvivo/glslViewer,patriciogonzalezvivo/glslViewer