mips64 n32 and n64 support in dl-machine.h

[Roland McGrath]

I would like someone else who knows the mips relocs to look at this patch too.
I don't know enough about mips to evaluate it.

I tend to think that either you should define ELF_MACHINE_RELA and not have
any #if'd out cruft in the file, or else just put your code in.  If it's
untested, that's ok for the time being.  Making prelink work is the test of
it, and that can get done before a glibc release with the new code.  If
making prelink work on mips is enough work that it needs to be put off
until later, then the elf_machine_rela code going into the sources can be
put off as well.  If time passes and there is bit rot, it seems to me that
copying the REL variant and fixing it up will be less error prone than
catching divergence between the two functions now that bit-rots in.