Freeze the rpmlib dependency set pool on successful return

- ...to avoid wasting memory on the relatively static data. We could
  handle the rpmlib ds singleton behavior here too but it would change
  semantics. Ponder about it later...
- Would be nicer to have rpmdsMerge() freeze on return, but that
  gets called in loops so we'd be doing a whole lot of huffing and
  puffing recreating the pools on each entry.

lib/rpmds.c

@@ -957,6 +957,8 @@ int rpmdsRpmlib(rpmds * dsp, const void * tblp)
 	rc = rpmdsMerge(dsp, ds);
 	rpmdsFree(ds);
     }
+    if (*dsp)
+	rpmstrPoolFreeze((*dsp)->pool);
     return rc;
 }