port d5f2ac5e (r37047)

  original commit message:
  Import base::ieee754::exp() from FreeBSD msun and introduce a Float64Exp
  TurboFan operator based on that, similar to what we do for Float64Log.
  Rewrite Math.exp() as TurboFan builtin and use that operator to also
  inline Math.exp() into optimized TurboFan functions.

BUG=

Review-Url: https://codereview.chromium.org/2096283002
Cr-Commit-Position: refs/heads/master@{#37269}