Major include refactor; changes to pretty much everything

This untangles some of the gigantic kitchen sink headers
in an attempt to split things into smaller files.
Also don't include gl.h, glext.h, windows.h,
and other such nonsense *everywhere*.

Lots of cleanups on the way too. More dead/unused code removal.

Remove incrFlag(), decrFlag() Lua functions.

ExternalLibs/GL/gl.h

@@ -31,18 +31,15 @@ extern "C" {
 ** the United States.
 */
 
-#ifndef APIENTRY
-#define APIENTRY
-#endif
 
 // BBGE HACK:
 // Because Win32 uses __declspec(dllimport) for OpenGL function imports,
-// although Core.cpp defines its own functions using the same names, which are just accessing
+// although GLLoad.cpp defines its own functions using the same names, which are just accessing
 // OpenGL function pointers acquired elsewhere, this leads to inconsistent linkage between
-// declaration in gl.h and the actual function definition in Core.cpp.
+// declaration in gl.h and the actual function definition in GLLoad.cpp.
 // So, we use this little hack to disable external linkage globally.
 #undef WINGDIAPI
-#define WINGDIAPI extern
+#define WINGDIAPI
 
 /*#ifndef WIN32
 #define WINGDIAPI
@@ -57,6 +54,10 @@ extern "C" {
 # define __DEFINED_GLAPI
 #endif
 
+#ifndef APIENTRY
+#define APIENTRY GLAPI
+#endif
+
 /*************************************************************/
 
 typedef unsigned int GLenum;

ExternalLibs/ttvfs_cfileapi/ttvfs_stdio.h

@@ -64,9 +64,7 @@ private:
 #elif VFS_ENABLE_C_API-0 == 0
 
 #include <stdio.h>
-#include <iostream>
-#include <fstream>
-#include <sstream>
+#include <iosfwd>
 typedef std::ifstream InStream;
 typedef FILE VFILE;