Update GLM to latest version (0.9.9.3). This includes GLM's change of matrices no longer default initializing to the identity matrix. This commit thus also includes the update of all of LearnOpenGL's code to reflect this: all matrices are now constructor-initialized to the identity matrix where relevant.

includes/glm/gtx/exterior_product.inl

@@ -0,0 +1,26 @@
+/// @ref gtx_exterior_product
+
+#include <limits>
+
+namespace glm {
+namespace detail
+{
+	template<typename T, qualifier Q, bool Aligned>
+	struct compute_cross_vec2
+	{
+		GLM_FUNC_QUALIFIER static T call(vec<2, T, Q> const& v, vec<2, T, Q> const& u)
+		{
+			GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'cross' accepts only floating-point inputs");
+
+			return v.x * u.y - u.x * v.y;
+		}
+	};
+}//namespace detail
+
+	template<typename T, qualifier Q>
+	GLM_FUNC_QUALIFIER T cross(vec<2, T, Q> const& x, vec<2, T, Q> const& y)
+	{
+		return detail::compute_cross_vec2<T, Q, detail::is_aligned<Q>::value>::call(x, y);
+	}
+}//namespace glm
+