Fix strtod for MSVC (#20490)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/20408. Tested locally by Jonas1312.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20490
Differential Revision: D15353137
Pulled By: ezyang
fbshipit-source-id: 0c0aefe54b11d50f703171700838af51f7666418
