Change by SteveH from original by John Denker (in the RT)

(Imported from upstream's 77ff1f3b8b)

Confirmed by inspection of source that this matches mozilla::pkix behavior. See
https://mxr.mozilla.org/mozilla-central/source/security/pkix/lib/pkixnames.cpp#939

Change-Id: Ic4e7d011f7c10cbc83e5267550063b0ebe9648fb
Reviewed-on: https://boringssl-review.googlesource.com/2848
Reviewed-by: Adam Langley <agl@google.com>

Windows has different names for these functions and also doesn't have
the strings.h header in which they appear.

This change adds tiny wrapper functions for Windows.

This change fixes a number of build warnings.

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)