Auto-generate RNA-structs declarations in RNA_prototypes.h

So far it was needed to declare a new RNA struct to `RNA_access.h` manually.
Since 9b298cf3db we generate a `RNA_prototypes.h` for RNA property
declarations. Now this also includes the RNA struct declarations, so they don't
have to be added manually anymore.

Differential Revision: https://developer.blender.org/D13862

Reviewed by: brecht, campbellbarton

source/blender/freestyle/intern/python/BPy_Freestyle.cpp

@@ -43,6 +43,7 @@ extern "C" {
 #include "DNA_scene_types.h"
 #include "FRS_freestyle.h"
 #include "RNA_access.h"
+#include "RNA_prototypes.h"
 #include "bpy_rna.h" /* pyrna_struct_CreatePyObject() */
 
 static char Freestyle_getCurrentScene___doc__[] =