PERF: Rewrite DoAddI() to avoid generating explicit check for overflow.

Revamp all the Add/AddP() macros so that they are consistent.
Add LRV, LRVH, STRV instructions to simulator
Fix endian issue in DoAddI
PERF: Add AHIK/AGHIK exploitation
use llilf for constant loading -- fix higher 32 bit in 64 bit mode
Add SubP(r,r,r) to MicroAssembler
replace Sub by SubP in RegExpMacroAssemblerS390::GetCode for address calulation