ClangFormat: apply to source, most of intern

Apply clang format as proposed in T53211.

For details on usage and instructions for migrating branches
without conflicts, see:

https://wiki.blender.org/wiki/Tools/ClangFormat

source/blender/gpu/GPU_immediate.h

@@ -145,4 +145,4 @@ void immActivate(void);
 void immDeactivate(void);
 void immDestroy(void);
 
-#endif  /* __GPU_IMMEDIATE_H__ */
+#endif /* __GPU_IMMEDIATE_H__ */