ShapeKey: add utils to say whether given ID type supports shapekeys.

Those kind of checks are handy to have for generic processing...

source/blender/blenkernel/BKE_key.h

@@ -66,6 +66,8 @@ float *BKE_key_evaluate_object_ex(
 float *BKE_key_evaluate_object(
         struct Object *ob, int *r_totelem);
 
+bool BKE_key_idtype_support(const short id_type);
+
 struct Key     **BKE_key_from_id_p(struct ID *id);
 struct Key      *BKE_key_from_id(struct ID *id);
 struct Key     **BKE_key_from_object_p(struct Object *ob);

source/blender/blenkernel/intern/key.c

@@ -1374,6 +1374,18 @@ float *BKE_key_evaluate_object(Object *ob, int *r_totelem)
 	return BKE_key_evaluate_object_ex(ob, r_totelem, NULL, 0);
 }
 
+bool BKE_key_idtype_support(const short id_type)
+{
+	switch (id_type) {
+		case ID_ME:
+		case ID_CU:
+		case ID_LT:
+			return true;
+		default:
+			return false;
+	}
+}
+
 Key **BKE_key_from_id_p(ID *id)
 {
 	switch (GS(id->name)) {