MIPS: Eliminate intentional conversion from Smi to Int32 in HMul

MIPS: Eliminate intentional conversion from Smi to Int32 in HMul

Port r16361 (b41ab14c)

Original commit message:
If not all uses of arithmetic binary operation can be truncated to Smi, check if they can be truncated to Int32 which could avoid minus zero check

Fixed DoMulI on X64 to adopt correct operand size when the representation is Smi

Fixed DoMulI on ARM. Constant right operand optimization is based on Integer 32 instead of its representation.

BUG=

Committed: https://code.google.com/p/v8/source/detail?r=16374

[palfia, 2013-08-27 21:42:51]

PTAL.

[Paul Lind, 2013-08-27 23:01:15]

LGTM.

[palfia, 2013-08-27 23:05:15]

Committed manually as r16374.