Thumb2 and ARM add/subtract with carry fixes.

Fixes Thumb2 ADCS and SBCS lowering: <rdar://problem/9275821>.
t2ADCS/t2SBCS are now pseudo instructions, consistent with ARM, so the
assembly printer correctly prints the 's' suffix.

Fixes Thumb2 adde -> SBC matching to check for live/dead carry flags.

Fixes the internal ARM machine opcode mnemonic for ADCS/SBCS.
Fixes ARM SBC lowering to check for live carry (potential bug).

llvm-svn: 130048