port ea925431 (r42545)

  original commit message:
  On ia32 return statements in C++ automatically convert signalling NaNs
  to quiet NaNs, even when bit_cast is used. This CL removes all uses of
  bit_cast<float> and bit_cast<double> in the wasm compiler and wasm
  interpreter.

BUG=

Review-Url: https://codereview.chromium.org/2648203002
Cr-Commit-Position: refs/heads/master@{#42588}