Tentative fix of GCC 6 tests

glm/detail/setup.hpp

@@ -283,7 +283,7 @@
 #else
 #	define GLM_HAS_CONSTEXPR ((GLM_LANG & GLM_LANG_CXX0X_FLAG) && GLM_HAS_INITIALIZER_LISTS && (\
 		((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_COMPILER >= GLM_COMPILER_INTEL17)) || \
-		((GLM_COMPILER & GLM_COMPILER_GCC) && (GLM_COMPILER >= GLM_COMPILER_GCC5)) || \
+		((GLM_COMPILER & GLM_COMPILER_GCC) && (GLM_COMPILER >= GLM_COMPILER_GCC6)) || \
 		((GLM_COMPILER & GLM_COMPILER_VC) && (GLM_COMPILER >= GLM_COMPILER_VC15))))
 #endif