* use a pool of MBState structures to speedup monoburg instead of using a
  mempool.
* the decode tables in the burg-generated could use short instead of int
  (this should save about 1 KB)
* track the use of ESP, so that we can avoid the x86_lea in the epilog


Other Ideas:

* the ORP people avoids optimizations inside catch handlers - just to save
  memory (for example allocation of strings - instead they allocate strings when
  the code is executed (like the --shared option)). But there are only a few
  functions using catch handlers, so I consider this a minor issue.