add portability variable for gnu sort and add coreutils to requirements
Fix update macros for gnutls and physfs

Fix "downdates" reported by Niels Kristian Bech Jensen for packages
gnutls and physfs by sorting version numbers properly and allowing
(in the case of gnutls) version number parts with more than one digit.
Update package libgomp

Set version number of libgomp to 4.8.0, as its source is contained in
the gcc sources anyway.
Merge pull request #169 from uklauer/updates

Fix some updates