adapt readme file

Signed-off-by: Nitload <Nitload_Creater@outlook.com>

tools/StgSharp.GenerateGL/xml/testglext.c

@@ -0,0 +1,27 @@
+/*% /lib/cpp -I../api testglext.c > testglext.i ; cc -c % ; rm testglext.[oi]
+*/
+#define GL_GLEXT_LEGACY
+#include <GL/gl.h>
+#define GL_GLEXT_PROTOTYPES
+#include "GL/glext.h"
+
+#define GLX_GLXEXT_LEGACY
+#include <GL/glx.h>
+
+/* Necessary to avoid token redefinition warnings */
+#undef GLX_SAMPLE_BUFFERS
+#undef GLX_SAMPLES
+#undef GLX_FRONT_EXT
+#undef GLX_BACK_EXT
+
+#define GLX_GLXEXT_PROTOTYPES
+#include "GL/glxext.h"
+
+int VERSION_4_3 = GL_VERSION_4_3;
+/* These should be the same */
+int mcsor = GL_MAX_COMBINED_SHADER_OUTPUT_RESOURCES;
+int mciufo = GL_MAX_COMBINED_IMAGE_UNITS_AND_FRAGMENT_OUTPUTS;
+
+/* See if latest extension is included */
+int latest_ext = GL_NV_blend_equation_advanced;
+GLenum latest_enum = GL_CONJOINT_NV;