* Fix file permissions race problem (CVE-2005-0953).
* Avoid possible segfault in BZ2_bzclose.
* Sanitise file names more carefully in bzgrep. Fixes CVE-2005-0758
to the extent that applies to bzgrep.
* Use 'mktemp' rather than 'tempfile' in bzdiff.
* Tighten up a couple of assertions in blocksort.c following automated
analysis.