port 7ceed92a (r36914)

  original commit message:
  Import base::ieee754::log1p() from fdlibm and introduce a Float64Log1p
  TurboFan operator based on that, similar to what we do for Float64Log.
  Rewrite Math.log1p() as TurboFan builtin and use that operator to also
  inline Math.log1p() into optimized TurboFan functions.

  Also unify the handling of the special IEEE 754 functions somewhat in
  the TurboFan backends. At some point we can hopefully express this
  completely in the InstructionSelector (once we have an idea what to do
  with the ST(0) return issue on IA-32/X87).

BUG=

  Drive-by-fix: Add some more test coverage for the log function.
Review-Url: https://codereview.chromium.org/2094953002

Cr-Commit-Position: refs/heads/master@{#37255}