Handling of -fpic in ASM_OUTPUT_MI_THUNK in sparc

[John Carr]

> Well, I suppose we could use call in all cases.  That would simplify the
> code.  Does anyone with more SPARC experience have an opinion?

On SPARC processors other than UltraSPARC call is at least as fast as
jmpl.  On UltraSPARC using a call without a matching return confuses
the return prediction stack.  It takes an extra 2-4 cycles to fetch
the correct set of instructions.  (For this reason, I think the recent
change to use call instead of rd %pc for V9 PIC was wrong even though
rd takes longer to execute.)

This is another thing we shouldn't be touching at so late in the
release cycle.  I have some changes I was planning to send after the
release.