CELL: use variant-length fragment ops programs

CELL: use variant-length fragment ops programs

This is a set of changes that optimizes the memory use of fragment
operation programs (by using and transmitting only as much memory as is
needed for the fragment ops programs, instead of maximal sizes), as well
as eliminate the dependency on hard-coded maximal program sizes.  State
that is not dependent on fragment facing (i.e. that isn't using
two-sided stenciling) will only save and transmit a single
fragment operation program, instead of two identical programs.

- Added the ability to emit a LNOP (No Operation (Load)) instruction.
  This is used to pad the generated fragment operations programs to
  a multiple of 8 bytes, which is necessary for proper operation of
  the dual instruction pipeline, and also required for proper SPU-side
  decoding.

- Added the ability to allocate and manage a variant-length
  struct cell_command_fragment_ops.  This structure now puts the
  generated function field at the end, where it can be as large
  as necessary.

- On the PPU side, we now combine the generated front-facing and
  back-facing code into a single variant-length buffer (and only use one
  if the two sets of code are identical) for transmission to the SPU.

- On the SPU side, we pull the correct sizes out of the buffer,
  allocate a new code buffer if the one we have isn't large enough,
  and save the code to that buffer.  The buffer is deallocated when
  the SPU exits.

- Commented out the emit_fetch() static function, which was not being used.