MIPS patch for relocateable output

[Ian Lance Taylor]

   Date: Sat, 17 Jul 1999 02:38:30 -0600 (MDT)
   From: "Mark P. Mitchell" <mark@codesourcery.com>

   This patch contains some additional tweaks to elflink.h to deal with
   multiple relocation sections.  It also restores the ld -r behavior in
   the MIPS back-end present before my recent changes.  (Except that that
   support was somewhat broken, I think; it apparently assigned GP a
   non-zero value for a relocateable object.)

Actually, it's OK to give GP a non-zero value for a relocateable
object.  Consider a relocateable object file with more than 0x8000
bytes of GP information.  We want a GP value which will work correctly
in that case.

The final link can retrieve the GP value of the input object from the
.reginfo or .option section.

   With this patch, there are no unexpeted failures on IRIX6.
   Furthermore, with Ian's help, I believe that there are no (known)
   issues in the MIPS back-end, relative to when I started my work.  My
   inspection did not real any further missing functionality, although I 
   may still have missed something.

   OK to check in?

It's OK with me.

Ian