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/ext/matrix_double4x2.hpp

@@ -0,0 +1,18 @@
+/// @ref core
+/// @file glm/ext/matrix_double4x2.hpp
+
+#pragma once
+#include "../detail/type_mat4x2.hpp"
+
+namespace glm
+{
+	/// @addtogroup core_matrix
+	/// @{
+
+	/// 4 columns of 2 components matrix of double-precision floating-point numbers.
+	///
+	/// @see <a href="http://www.opengl.org/registry/doc/GLSLangSpec.4.20.8.pdf">GLSL 4.20.8 specification, section 4.1.6 Matrices</a>
+	typedef mat<4, 2, double, defaultp>		dmat4x2;
+
+	/// @}
+}//namespace glm