GCC: Fix noexcept warnings on hash functions

Fix warnings on hash functions with GCC and -Wnoexcept:
* Add GLM_HAS_NOEXCEPT flag & GLM_NOEXCEPT #define to setup.hpp.
* Add GLM_NOEXCEPT to hash functions in hash.hpp.
* Add GLM_NOEXCEPT to matrix operator[] accessors.
* Add gtx_hash.cpp and a test to verify all hash overloads compile.
  Configure with -DCMAKE_CXX_FLAGS="-Werror -Wnoexcept" to test.

test/gtx/CMakeLists.txt

@@ -18,6 +18,7 @@ glmCreateTestGTC(gtx_fast_trigonometry)
 glmCreateTestGTC(gtx_functions)
 glmCreateTestGTC(gtx_gradient_paint)
 glmCreateTestGTC(gtx_handed_coordinate_space)
+glmCreateTestGTC(gtx_hash)
 glmCreateTestGTC(gtx_integer)
 glmCreateTestGTC(gtx_intersect)
 glmCreateTestGTC(gtx_io)

test/gtx/gtx_hash.cpp

@@ -0,0 +1,55 @@
+#define GLM_ENABLE_EXPERIMENTAL
+#include <glm/gtx/hash.hpp>
+#include <unordered_map>
+
+int test_compile()
+{
+	int Error = 0;
+
+    // Vector types
+    std::unordered_map<glm::vec1, int> map_vec1;
+    Error += ++map_vec1[glm::vec1(0.0f)];
+    std::unordered_map<glm::vec2, int> map_vec2;
+    Error += ++map_vec2[glm::vec2(0.0f)];
+    std::unordered_map<glm::vec3, int> map_vec3;
+    Error += ++map_vec3[glm::vec3(0.0f)];
+    std::unordered_map<glm::vec4, int> map_vec4;
+    Error += ++map_vec4[glm::vec4(0.0f)];
+
+    // Quaternion types
+    std::unordered_map<glm::quat, int> map_quat;
+    Error += ++map_quat[glm::quat(0.0f, glm::vec3(0.0f))];
+    std::unordered_map<glm::dualquat, int> map_dualquat;
+    Error += ++map_dualquat[glm::dualquat(glm::vec3(0.0f))];
+
+    // Matrix types
+    std::unordered_map<glm::mat2x2, int> map_mat2x2;
+    Error += ++map_mat2x2[glm::mat2x2(0.0f)];
+    std::unordered_map<glm::mat2x3, int> map_mat2x3;
+    Error += ++map_mat2x3[glm::mat2x3(0.0f)];
+    std::unordered_map<glm::mat2x4, int> map_mat2x4;
+    Error += ++map_mat2x4[glm::mat2x4(0.0f)];
+    std::unordered_map<glm::mat3x2, int> map_mat3x2;
+    Error += ++map_mat3x2[glm::mat3x2(0.0f)];
+    std::unordered_map<glm::mat3x3, int> map_mat3x3;
+    Error += ++map_mat3x3[glm::mat3x3(0.0f)];
+    std::unordered_map<glm::mat3x4, int> map_mat3x4;
+    Error += ++map_mat3x4[glm::mat3x4(0.0f)];
+    std::unordered_map<glm::mat4x2, int> map_mat4x2;
+    Error += ++map_mat4x2[glm::mat4x2(0.0f)];
+    std::unordered_map<glm::mat4x3, int> map_mat4x3;
+    Error += ++map_mat4x3[glm::mat4x3(0.0f)];
+    std::unordered_map<glm::mat4x4, int> map_mat4x4;
+    Error += ++map_mat4x4[glm::mat4x4(0.0f)];
+
+	return Error > 0 ? 0 : 1;
+}
+
+int main()
+{
+	int Error = 0;
+
+	Error += test_compile();
+
+	return Error;
+}