Gnus -- Compatability "fix" (well... "improvement")

In my book, anything that allows for stuff in Gnus' sxepkg.el to be
deleted is a good thing.  SXEmacs'
'define-obsolete-(function|variable)-alias' functions now take 2 - 4
args to make them compat with GNU's 3 - 4 arg versions.

This does mean though, that to compile (not run) packages you will
need at least SXEmacs v22.1.16-44-g1197b37

* gnus-fix:
  Gnus -- Remove some no longer needed compatibility cruft.
  Revert "Gnus -- temporary workaround to allow other pkgs to build."