Merge latest changes from http://www.netlib.org/fp/dtoa.c into dtoa.cc

This fixed crbug.com/588726 infinite loop issue and also eliminated
previous local patch for crbug.com/123157 crash issue.

BUG=588726
TEST=base_unittests: pass all cases with asan and ubsan_security; pass StringNumberConversionsTest with msan.

Review-Url: https://codereview.chromium.org/2364123002
Cr-Commit-Position: refs/heads/master@{#420825}
5 files changed