Two modifications:
1. The addition of 2013 to the copyright year range for every file;
2. The use of a single year range, instead of potentially multiple
year ranges, as approved by the FSF.
(make_cleanup_dtor_ftype): New typedef.
(make_cleanup_dtor): Use it.
(ALL_CLEANUPS): Replace with ...
(all_cleanups): ... this. Declare. All uses updated.
* cleanups.c: #include "gdb_assert.h".
(sentinel_cleanup): New static global.
(SENTINEL_CLEANUP): Define.
(cleanup_chain, final_cleanup_chain): Initialize to SENTINEL_CLEANUP.
(make_my_cleanup2): Assert result is non-NULL.
(all_cleanups): New function.
(save_my_cleanups): Initialize new chain to SENTINEL_CLEANUP instead
of NULL.
