Added imapfilter
Added openconnect
Added heimdal 1.5.2, keeping version 1.3.3
Added rxvt_unicode_with_perl
rxvt_unicode with perl extension enabled by default
grouped heimdal versions in all_packages.nix
heimdal: remove obsolete 1.3.x version
heimdal: cosmetic to make syntax highlightig happy
all-packages.nix: drop trailing whitespace