core regs vs. proc-service regs mess

["David S. Miller" <davem@davemloft.net>]

In trying to get core files working properly again on Linux/Sparc and
Daniel I now see the problems you referred to the other day.

What we have currently on Linux/Sparc is:

1) ptrace() interfaces have one layout for regsets
2) ELF core files store regsets in a different
   format

Now proc-service.c wants fill_gregset() et al. to
provide things in the ptrace() style layout, that is
what libthread_db expects under Linux.

But linux_nat_make_corefile_notes() expects the fill_gregset()
et al. to provide ELF core file format registers.

This is completely contradictory, and I don't have any idea how to
cleanly resolve this outside of duplicating the entirety of
linux_nat_make_corefile_notes() on Linux/Sparc which is silly.

Daniel any ideas? :-) Maybe we can have a "linux_tdep" struct where we
can place a "->to_fill_core_gregset()" type method or similar?