[turbofan] Fix HashCode/Equals for floating point operators.

[turbofan] Fix HashCode/Equals for floating point operators.

Those floating point constant operators require bitwise handling of
their parameters, otherwise 0.0 equals -0.0. This is solved in a
general way by adding new base::bit_equal_to and base::bit_hash
function objects.

TEST=unittests
R=svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=24450

[Benedikt Meurer, 2014-10-08 05:53:11]

bmeurer@chromium.org changed reviewers:
- jarin@chromium.org

[Benedikt Meurer, 2014-10-08 05:54:26]

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

[Benedikt Meurer, 2014-10-08 05:54:27]

PTAL

[Benedikt Meurer, 2014-10-08 05:56:34]

https://codereview.chromium.org/636953002/diff/20001/src/base/functional.h
File src/base/functional.h (right):

https://codereview.chromium.org/636953002/diff/20001/src/base/functional.h#ne...
src/base/functional.h:71: return hash_combine(hash_combine(vs...),
hash<T>()(v));
Reordered because we pass the seed as first parameter, and we don't need to
rehash the seed, therefore we want it to use the size_t specialization of
hash_combine.

[Sven Panne, 2014-10-08 06:53:47]

lgtm

[Benedikt Meurer, 2014-10-08 07:32:17]

Committed patchset #3 (id:40001) manually as 24450 (presubmit successful).