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.

m4/.cvsignore

@@ -30,6 +30,7 @@ dirname.m4
 dos.m4
 double-slash-root.m4
 dup2.m4
+eaccess.m4
 eealloc.m4
 eoverflow.m4
 error.m4
@@ -44,6 +45,7 @@ file-type.m4
 fileblocks.m4
 filemode.m4
 filenamecat.m4
+findprog.m4
 flexmember.m4
 fnmatch.m4
 fpending.m4

m4/.gitignore

@@ -29,6 +29,7 @@ dirname.m4
 dos.m4
 double-slash-root.m4
 dup2.m4
+eaccess.m4
 eealloc.m4
 eoverflow.m4
 error.m4
@@ -43,6 +44,7 @@ file-type.m4
 fileblocks.m4
 filemode.m4
 filenamecat.m4
+findprog.m4
 flexmember.m4
 fnmatch.m4
 fpending.m4