32->64 bit cross compilers

[dewar@gnat.com]

<<I think it would be *nice*, but I don't think we "have to".  This never
really worked right due to config files that didn't properly check
the bounds of constants, mostly in the older machines.  So I don't
think it's so terrible if it still doesn't, especially since changes to
fix these things can easily cause instability.
>>

Oops, of course I meant to say GNU/Linux -> 64-bit Sparc cross-compilation
(the inclination to abbreviate when typing in text fast in email mode is
hard to resist :-)