Ghost Context Refactor

https://developer.blender.org/D643
Separates graphics context creation from window code in Ghost so that they can vary separately.

source/blender/gpu/intern/gpu_codegen.c

@@ -31,7 +31,7 @@
  * Convert material node-trees to GLSL.
  */
 
-#include "GL/glew.h"
+#include "GPU_glew.h"
 
 #include "MEM_guardedalloc.h"
 
@@ -242,12 +242,12 @@ GPUFunction *GPU_lookup_function(const char *name)
 	return (GPUFunction*)BLI_ghash_lookup(FUNCTION_HASH, (void *)name);
 }
 
-void GPU_codegen_init(void)
+void gpu_codegen_init(void)
 {
 	GPU_code_generate_glsl_lib();
 }
 
-void GPU_codegen_exit(void)
+void gpu_codegen_exit(void)
 {
 	extern Material defmaterial;    // render module abuse...