New packages: pam_mount and libHX

Add pam_mount package. Integration into NixOS is still missing.
Merge branch 'upstream' into pam_mount

Conflicts:
	pkgs/top-level/all-packages.nix
Fix description in pam_mount and libHX. Add tstrobel as maintainer.
Merge pull request #4092 from ts468/pam_mount

New packages: pam_mount and libHX