added index to ParentID on prims, as this is sorted on for prim loading.

This should speed up initial load of prims, especially on primy regions.

OpenSim/Data/MySQL/Resources/012_RegionStore.sql

@@ -0,0 +1,5 @@
+BEGIN;
+
+ALTER TABLE prims add index prims_parentid(ParentID);
+
+COMMIT;