Log Message:
Updated tarsnap to 1.0.39.

Tarsnap 1.0.39 is now available.  (Yes, just 2 weeks after 1.0.38.)  This
version brings several important bug fixes:

* tarsnap 1.0.38 (but not earlier versions) would exit with an assertion
failure after successfully creating an archive containing a file with a
"last modified" time prior to January 1st, 1970.

* tarsnap 1.0.38 and earlier could crash if instructed to archive the
contents of corrupt cpio or ar archives (via the @archive directive).

* tarsnap 1.0.38 and earlier could crash if passed an invalidly encrypted
key file.