Added SDL_VIDEO_OPENGL_ES2 to the SDL_config.h templates (Thanks, Kerim!).

include/SDL_config.h.cmake

@@ -288,6 +288,7 @@
 /* Enable OpenGL support */
 #cmakedefine SDL_VIDEO_OPENGL @SDL_VIDEO_OPENGL@
 #cmakedefine SDL_VIDEO_OPENGL_ES @SDL_VIDEO_OPENGL_ES@
+#cmakedefine SDL_VIDEO_OPENGL_ES2 @SDL_VIDEO_OPENGL_ES2@
 #cmakedefine SDL_VIDEO_OPENGL_BGL @SDL_VIDEO_OPENGL_BGL@
 #cmakedefine SDL_VIDEO_OPENGL_CGL @SDL_VIDEO_OPENGL_CGL@
 #cmakedefine SDL_VIDEO_OPENGL_GLX @SDL_VIDEO_OPENGL_GLX@

include/SDL_config.h.in

@@ -289,6 +289,7 @@
 /* Enable OpenGL support */
 #undef SDL_VIDEO_OPENGL
 #undef SDL_VIDEO_OPENGL_ES
+#undef SDL_VIDEO_OPENGL_ES2
 #undef SDL_VIDEO_OPENGL_BGL
 #undef SDL_VIDEO_OPENGL_CGL
 #undef SDL_VIDEO_OPENGL_EGL