* src/files.c (tr): Change return type to void.

* src/muscle_tab.c (muscle_insert): Free storage in case muscle_grow
has been called previously for the same key.
(muscle_find): Return storage instead of value so that
--enable-gcc-warnings doesn't produce warnings that the return discards
const.  aver that the value and storage are the same since storage
could potentially be NULL when value is not.
* tests/testsuite.at (AT_CHECK): Treat an unspecified exit value the
same as 0.

src/files.c

@@ -137,7 +137,7 @@ xfclose (FILE *ptr)
 `------------------------------------------------------------------*/
 
 /* In the string S, replace all characters FROM by TO.  */
-static char *
+static void
 tr (char *s, char from, char to)
 {
   for (; *s; s++)