Removed obsolete extension definitions

Fixes https://github.com/libsdl-org/SDL/issues/6231

include/SDL_opengl.h

@@ -2107,57 +2107,6 @@ typedef void (APIENTRYP PFNGLMULTITEXCOORD4SVARBPROC) (GLenum target, const GLsh
 
 
 
-/*
- * ???. GL_MESA_packed_depth_stencil
- * XXX obsolete
- */
-#ifndef GL_MESA_packed_depth_stencil
-#define GL_MESA_packed_depth_stencil 1
-
-#define GL_DEPTH_STENCIL_MESA			0x8750
-#define GL_UNSIGNED_INT_24_8_MESA		0x8751
-#define GL_UNSIGNED_INT_8_24_REV_MESA		0x8752
-#define GL_UNSIGNED_SHORT_15_1_MESA		0x8753
-#define GL_UNSIGNED_SHORT_1_15_REV_MESA		0x8754
-
-#endif /* GL_MESA_packed_depth_stencil */
-
-
-#ifndef GL_ATI_blend_equation_separate
-#define GL_ATI_blend_equation_separate 1
-
-#define GL_ALPHA_BLEND_EQUATION_ATI	        0x883D
-
-GLAPI void GLAPIENTRY glBlendEquationSeparateATI( GLenum modeRGB, GLenum modeA );
-typedef void (APIENTRYP PFNGLBLENDEQUATIONSEPARATEATIPROC) (GLenum modeRGB, GLenum modeA);
-
-#endif /* GL_ATI_blend_equation_separate */
-
-
-/* GL_OES_EGL_image */
-#ifndef GL_OES_EGL_image
-typedef void* GLeglImageOES;
-#endif
-
-#ifndef GL_OES_EGL_image
-#define GL_OES_EGL_image 1
-#ifdef GL_GLEXT_PROTOTYPES
-GLAPI void APIENTRY glEGLImageTargetTexture2DOES (GLenum target, GLeglImageOES image);
-GLAPI void APIENTRY glEGLImageTargetRenderbufferStorageOES (GLenum target, GLeglImageOES image);
-#endif
-typedef void (APIENTRYP PFNGLEGLIMAGETARGETTEXTURE2DOESPROC) (GLenum target, GLeglImageOES image);
-typedef void (APIENTRYP PFNGLEGLIMAGETARGETRENDERBUFFERSTORAGEOESPROC) (GLenum target, GLeglImageOES image);
-#endif
-
-
-/**
- ** NOTE!!!!!  If you add new functions to this file, or update
- ** glext.h be sure to regenerate the gl_mangle.h file.  See comments
- ** in that file for details.
- **/
-
-
-
 /**********************************************************************
  * Begin system-specific stuff
  */