- untangled r_defs.h from actor.h

Both files can now be included independently without causing problems.
This also required moving some inline functions into separate files and splitting off the GC definitions from dobject.h to ensure that r_defs does not need to pull in any part of the object hierarchy.

src/r_data/renderstyle.cpp

@@ -35,6 +35,7 @@
 #include "templates.h"
 #include "renderstyle.h"
 #include "c_cvars.h"
+#include "serializer.h"
 
 CVAR (Bool, r_drawtrans, true, 0)
 CVAR (Int, r_drawfuzz, 1, CVAR_ARCHIVE)
@@ -191,3 +192,8 @@ void FRenderStyle::CheckFuzz()
 		BlendOp = STYLEOP_Fuzz;
 	}
 }
+
+FSerializer &Serialize(FSerializer &arc, const char *key, FRenderStyle &style, FRenderStyle *def)
+{
+	return arc.Array(key, &style.BlendOp, def ? &def->BlendOp : nullptr, 4);
+}