debmirror.py bugfix: output package prefixes in alphabetical order
debmirror.py bugfix: output package prefixes in alphabetical order

this fixes the random ordering of prefixes on the front page

oorestisime/debsources,Debian/debsources,matthieucan/debsources,oorestisime/debsources,oorestisime/debsources,Debian/debsources,nonas/debian-qa,nonas/debian-qa,vivekanand1101/debsources,oorestisime/debsources,matthieucan/debsources,clemux/debsources,devoxel/debsources,clemux/debsources,matthieucan/debsources,Debian/debsources,nonas/debian-qa,vivekanand1101/debsources,sophiejjj/debsources,clemux/debsources,vivekanand1101/debsources,vivekanand1101/debsources,oorestisime/debsources,sophiejjj/debsources,matthieucan/debsources,devoxel/debsources,sophiejjj/debsources,clemux/debsources,devoxel/debsources,zacchiro/debsources,Debian/debsources,devoxel/debsources,devoxel/debsources,sophiejjj/debsources,sophiejjj/debsources,zacchiro/debsources,nonas/debian-qa,clemux/debsources,vivekanand1101/debsources,Debian/debsources,zacchiro/debsources,zacchiro/debsources,matthieucan/debsources,zacchiro/debsources