[turbofan] Introduce WordRor machine operator.

[turbofan] Introduce WordRor machine operator.

Move recognition of rotate-right operations to the
MachineOperatorReducer, so we don't need to repeat that in the
InstructionSelector for every backend.

TEST=base-unittests,compiler-unittests,cctests
R=jarin@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=23121

[Benedikt Meurer, 2014-08-14 08:46:36]

PTAL

[Jarin, 2014-08-14 09:06:05]

lgtm with one comment - please update the .gn file.

[Benedikt Meurer, 2014-08-14 09:07:02]

Done.

[Benedikt Meurer, 2014-08-14 09:08:20]

Committed patchset #2 manually as 23121 (tree was closed).