RepoUmask fixes

Writing the description and git-daemon-export-ok files needs to be done
using textfile() which will honour the RepoUmask.

If you have global umask 0077 and a specific repo with 0022, then the
description and git-daemon-export-ok files would previously get written
with mode 0600, when they should be 0644.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Tested-by: Robin H. Johnson <robbat2@gentoo.org>
amendments to previous commit about honoring repoumask

-   convert git-daemon access list trigger from sh to perl.  There's not much
    shell code in there now anyway

-   (minor) use \t as the separator in the description file update code