Add missing newline to error messages

Also improve the message style a bit while we're here.

src/bin/pg_dump/pg_dump.c

@@ -9657,7 +9657,7 @@ dumpCast(Archive *fout, CastInfo *cast)
 	{
 		funcInfo = findFuncByOid(cast->castfunc);
 		if (funcInfo == NULL)
-			exit_horribly(NULL, "unable to find function definition for OID %u",
+			exit_horribly(NULL, "could not find function definition for function with OID %u\n",
 						  cast->castfunc);
 	}