This updates man-db to the latest release, 2.7.6.1.

I tested that the manual-database profile hook still works. For that, I
had to pass the new configuration option 'disable-cache-owner', or else
the test suite and manpage database generation would fail.

See this commit for more info (Separate cache owner from --enable-setuid
option):

https://git.savannah.gnu.org/cgit/man-db.git/commit/?id=0f8b5518949866075c25787bdc4e9c064597c21e