expand sharing of shadow translation across more cases

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on December 10, 2010 17:58:09_

PR 494727

this is an extension of the initial sharing impl in PR 493257

we should also try to share across:
- mem2mem (in particular push-mem, pop-mem, and call-ind)
- sub-dword
- app instr that reads/writes both whole-bb reg1 and reg2
- app instr that does not share same memref: start w/
simple instrs like reg-reg moves by having them use reg2.
initial goal can be this common pattern:
push ebp, mov esp->ebp, push edi, push esi, push ebx

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=165_