Drop unused rdtsc instruction.

Drop unused rdtsc instruction.

We do not use rdtsc anywhere and we won't ever use that in the
future, as it is totally unusable with multicore and out of
order execution.

R=jkummerow@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16268

[Benedikt Meurer, 2013-08-22 11:10:09]

PTAL, red-only :-)

[Jakob Kummerow, 2013-08-22 11:52:36]

LGTM due to the difficulty in using RDTSC properly.

For the record, I'm generally against removing instructions our assembler
supports, even if they're currently unused.

[Benedikt Meurer, 2013-08-22 11:58:34]

Committed patchset #1 manually as r16268.