build failure on Irix 6.5/gcc

[Dave Love]

I've reported the longstanding failure to build on Irix 6.5 before,
and I assume you're not interested.  However, I'm going to lose access
to the platform, so I'm reporting the currently-working solution.
Also experience suggests the same issue will bite GNU systems
eventually.

Building with gcc 3.4, it segvs when dumping due to the usual unexec
lossage.  unexelf.c needs to copy the additional sections .data.rel
and .data.rel.local.  Entries in gcc 3.4's varasm.c suggest it should
also copy .data.rel.ro, .data.rel.ro.local, .tdata, .sdata2 and .tbss;
an expert should comment on that, though.

There are warnings that the definitions of XUINT, XSET in iris4d.h are
clobbered by lisp.h.  I don't know what should happen about those.

Also, this config should not have NO_REMAP defined (in iris4d.h, where
it could be conditional on IRIX6_5) and it should define
GC_SETJMP_WORKS and GC_MARK_STACK in irix6-5.h as in irix6-0.h.  (I
don't understand how I left it in that state, but all the config
system is so messy it's easy to do.)  I assume NO_REMAP should also be
undefined on GNU MIPS systems (and others?).