This way we avoid the second deoptimization for the Math.floor and
Math.ceil builtins when -0 is involved. We still deoptimize the inlined
Crankshaft version in various cases, that's a separate issue.

The algorithm used for implement CodeStubAssembler::Float64Floor is
vaguely based on the fast math version used in the libm of various BSDs,
but had to be reengineered to match the EcmaScript specification.

R=epertoso@chromium.org
BUG=v8:2890, v8:4059
LOG=n

Review URL: https://codereview.chromium.org/1828253002

Cr-Commit-Position: refs/heads/master@{#35083}