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/quaternion_double.hpp

@@ -0,0 +1,39 @@
+/// @ref ext_quaternion_double
+/// @file glm/ext/quaternion_double.hpp
+///
+/// @defgroup ext_quaternion_double GLM_EXT_quaternion_double
+/// @ingroup ext
+///
+/// Exposes double-precision floating point quaternion type.
+///
+/// Include <glm/ext/quaternion_double.hpp> to use the features of this extension.
+///
+/// @see ext_quaternion_float
+/// @see ext_quaternion_double_precision
+/// @see ext_quaternion_common
+/// @see ext_quaternion_exponential
+/// @see ext_quaternion_geometric
+/// @see ext_quaternion_relational
+/// @see ext_quaternion_transform
+/// @see ext_quaternion_trigonometric
+
+#pragma once
+
+// Dependency:
+#include "../detail/type_quat.hpp"
+
+#if GLM_MESSAGES == GLM_ENABLE && !defined(GLM_EXT_INCLUDED)
+#	pragma message("GLM: GLM_EXT_quaternion_double extension included")
+#endif
+
+namespace glm
+{
+	/// @addtogroup ext_quaternion_double
+	/// @{
+
+	/// Quaternion of double-precision floating-point numbers.
+	typedef qua<double, defaultp>		dquat;
+
+	/// @}
+} //namespace glm
+