[turbofan] Add backend support for load/store float32 values.

[turbofan] Add backend support for load/store float32 values.

This is the bare minimum required to support typed arrays. Support for
working with float32 values will be added based on this.

TEST=compiler-unittests,cctest
R=svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=23386

[Benedikt Meurer, 2014-08-26 06:00:43]

bmeurer@chromium.org changed reviewers:
+ svenpanne@chromium.org

[Benedikt Meurer, 2014-08-26 06:00:43]

PTAL

[Sven Panne, 2014-08-26 06:43:23]

lgtm

[Benedikt Meurer, 2014-08-26 08:29:33]

Committed patchset #2 manually as 23386 (presubmit successful).