Remove OpenGL headers from video_context as it doesn't touch OpenGL anymore

Originally committed to SVN as r5905.

aegisub/src/video_context.cpp

@@ -46,14 +46,6 @@
 #include <wx/msgdlg.h>
 #endif
 
-#ifdef __APPLE__
-#include <OpenGL/gl.h>
-#include <OpenGL/glu.h>
-#else
-#include <GL/gl.h>
-#include <GL/glu.h>
-#endif
-
 #include <libaegisub/access.h>
 #include <libaegisub/keyframe.h>
 

aegisub/src/video_context.h

@@ -40,15 +40,10 @@
 #include <list>
 #include <memory>
 
-#include <wx/glcanvas.h>
 #include <wx/timer.h>
 #include <wx/stopwatch.h>
 #endif
 
-#if ! wxUSE_GLCANVAS
-#error "Aegisub requires wxWidgets to be compiled with OpenGL support."
-#endif
-
 #include <libaegisub/signal.h>
 #include <libaegisub/vfr.h>
 

aegisub/src/visual_tool.cpp

@@ -24,7 +24,6 @@
 
 #ifndef AGI_PRE
 #include <algorithm>
-#include <wx/glcanvas.h>
 #endif
 
 #include "visual_tool.h"