Copy libffi from sxemacs

[Stephen J. Turnbull]

Aidan Kehoe writes:
 > 
 >  Ar an dara lá de mí Meitheamh, scríobh Jeff Sparkes: 
 > 
 >  > Now that RMS has approved GCC's use of dynamically loading plugins, we
 >  > should add FFI to xemacs.
 > 
 > RMS' decision on this is irrelevant to us, his delay over this decision is
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 > why we have #'load-module and GNU doesn?t. 
 > 
 >  > My understanding is that the sxemacs uses libffi for this.  Could this
 >  > easily be copied into XEmacs?
 > 
 > Relatively easily; see http://hg.debian.org/hg/xemacs/xemacs-ffi/ . I
 > couldn't get that to run on OS X a few months ago, though I imagine it works
 > on Linux. More work needed.

Hm.  IIRC, at the time I committed the code it worked out of the box
(ie, built, ran, and curl.el fetched http://www.xemacs.org/index.html
OK) on OS X 10.4, OS X 10.5, and Gentoo Linux.  OS X 10.4 required
installing libffi via MacPorts and use of a particular version of GCC,
probably MacPorts gcc42.  I forget whether 10.5 needed special
treatment, it may have needed a MacPorts GCC too.

I'll try to get back to that next week and report on whether I can get
at least that far at this point.