[ nedit-Bugs-1048304 ] Very slow resizing of Nedit window on Xorg 6.8

[Scott Tringali]

I see we've got the XLIB_SKIP_ARGB_VISUALS in there, but I think someone 
ran into that not helping when X is remote.

Should we just skip any visual deeper than 24 bits? Or is there a reason 
that won't work?

Or, we can skip the search when the default visual is not 8 bits. 
That's all this code is for anyway.  NEdit isn't very color intensive 
and a 16-bit visual usually is enough.