optimisation for default_print_insn().

[Doug Evans]

matthew green writes:
 > i've been looking at the cgen generated disassemblers lately
 > and i've noticed that it reads target memory twice for the
 > initial portion of the instruction.  in default_print_insn(),
 > there is a call to (*info->read_memory_func)() and then it
 > calls print_insn().  the first thing print_insn() does is
 > call read_insn() which performs the exact same read_memory_func
 > call (same arguments, buffers, etc.)  as read_insn() is used 
 > in other places, i believe the best way to fix this double
 > read is to remove the copy in default_print_insn().  i have
 > tested this with a couple of ports and nothing appeas to be
 > broken.
 > 
 > 
 > the patch below simply comments the block in
 > default_print_insn() rather than removing it entirely.  if
 > people think it should be removed, i can change my patch.

Assuming your patch goes in, don't use #if 0's.
They just reduce the signal/noise ratio.
[sometimes they're ok, but not in this case]

 > OK to commit?

I'd rather not.  Studying the code, the comment above print_insn,
and the m32r port makes it seem to me that the read_insn
at the start of print_insn is the duplicate.
Why was it added?