turn gc of unused data/code back on in loaders.

turned it off while debugging 8 runtime problem,
checked in the change accidentally.

R=r
DELTA=4  (0 added, 0 deleted, 4 changed)
OCL=27040
CL=27046

src/cmd/ld/go.c

@@ -581,7 +581,7 @@ deadcode(void)
 	mark(lookup(INITENTRY, 0));
 	mark(lookup("sys·morestack", 0));
 
-//	sweeplist(&firstp, &lastp);
-//	sweeplist(&datap, &edatap);
+	sweeplist(&firstp, &lastp);
+	sweeplist(&datap, &edatap);
 }