RNA

* DNA_radio_types.h: done. (patch by Jorge Bernal). Also adds
  some #defines in the radiosity DNA since it was using hardcoded
  values.
* Added an "UnknownType" which has no properties, useful as a
  placeholder for pointers that have no defined type yet.
* Sort a few lists in the code alphabetically.

source/blender/makesrna/intern/rna_ID.c

@@ -185,6 +185,9 @@ static void rna_def_library(BlenderRNA *brna)
 }
 void RNA_def_ID(BlenderRNA *brna)
 {
+	/* simple built-in unknown type */
+	RNA_def_struct(brna, "UnknownType", NULL, "Unknown Type");
+
 	rna_def_ID(brna);
 	rna_def_ID_properties(brna);
 	rna_def_library(brna);