[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

Review URL: https://codereview.chromium.org/636953002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24450 ce2b1a6d-e550-0410-aec6-3dcde31c8c00