Modified the unix_chkpwd utility to allow the git user to check passwords, enabling gitlab to use pam

To install just the modified binary do the following:

sudo apt-get install build-essential fakeroot devscripts equivs lintian
sudo apt-get build-dep pam
fakeroot debian/rules binary
sudo cp ./debian/tmp/sbin/unix_chkpwd /sbin/unix_chkpwd

The git user will now be able to use pam authenticaiton for gitlab or any other git server/