64-bit lossage

[Dave Love]

It looks as though the current code is broken generally on 64-bit
systems (by induction from alpha-osf and mips-sgi, so not
endian-related).  I don't know since when, but it predates the
emacs-unicode branch, which it's hampering me working on.  The symptom
is a crash (segv, if I remember correctly) in GC during dumping.

I made a bug report some time ago, but it doesn't seem to have been
fixed.  Could someone look into it?  I assume the commercial outfits
(at least SuSE?) are interested in 64-bit.

(It isn't due to an obvious lack of prototypes, although I found and
fixed a few on the unicode branch.)