Merge branch 'master' into docking

# Conflicts:
#	docs/CHANGELOG.txt
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp

examples/imgui_impl_opengl3.h

@@ -23,6 +23,7 @@
 //  Only override if your GL version doesn't handle this GLSL version. See GLSL version table at the top of imgui_impl_opengl3.cpp.
 
 #pragma once
+#include "imgui.h"      // IMGUI_IMPL_API
 
 // Backend API
 IMGUI_IMPL_API bool     ImGui_ImplOpenGL3_Init(const char* glsl_version = NULL);