more qbuf

Pat pointed out to me that there are other potential
qbuf overflows, so this adds a function to assist in
weeding them out.

include/extern.h

@@ -1478,6 +1478,7 @@ E int NDECL(doloot);
 E int FDECL(use_container, (struct obj *,int));
 E int FDECL(loot_mon, (struct monst *,int *,boolean *));
 E int NDECL(dotip);
+E char *FDECL(safe_qbuf, (char *,unsigned,char *,char *,const char *));
 
 /* ### pline.c ### */