Pass "make distcheck" again.
* src/sort.c (usage): Split a diagnostic that had grown to be
longer than the C89 maximum of 509 bytes.
* .x-sc_cast_of_argument_to_free: New file. Allow a cast in sort.c.
FIXME: this is just temporary, while we wait to remove the offending
access-calling code.
* Makefile.am (EXTRA_DIST): Add .x-sc_cast_of_argument_to_free.
* Makefile.maint (sc_cast_of_argument_to_free): Use the
canonical, $$($(CVS_LIST_EXCEPT)).
* m4/.gitignore, m4/.cvsignore, lib/.gitignore, lib/.cvsignore: Update.