[PATCH/mips] mips16 frame code simplification

[Joel Brobecker <brobecker@gnat.com>]

(Andrew, if you could look at this change, just to make sure there's
no obvious screwup. Thanks!)

This is the mips16 counterpart of a simplification I made on 2004-09-14
for mips32:

        http://sources.redhat.com/ml/gdb-patches/2004-09/msg00245.html

2004-10-10  Joel Brobecker  <brobecker@gnat.com>

        * mips-tdep.c (mips16_decode_reg_save): Delete, no longer used.
        (mips_insn16_frame_cache): Pass frame cache in call to
        heuristic_proc_desc. Move some code to mips16_heuristic_proc_desc.
        Remove code that became redundant as a consequence.
        (mips32_heuristic_proc_desc): No longer compute a fake
        procedure descriptor. Compute the full frame cache instead.
        Some minor comment reformatting.

Not having a mips16 target handy, I couldn't test this change.
However, it just basically did the same work than I did for mips32,
with extra care as to what I was doing. And I also verified that this
code still builds.

This should open the door to further cleanups in this file.

Comitted,
-- 
Joel