On all Windows platforms, not just Cygwin, use _timezone and _tzname.
Back-patch commit
868628e4f into the 9.5 branch, so that we can support
building that branch with Visual Studio 2015. This patch itself could
go further back, but other VS2015 patches such as
0fb54de9a and
c8e81afc6
were only back-patched to 9.5, so there seems little point in handling
this one differently.
Discussion: https://postgr.es/m/CAD=LzWFg+Z-KUS3Wm8-1J2vOuYErJXbjuE6b7quzswQEBXJWMQ@mail.gmail.com
Now that we have backported VS2015 support to 9.4 and 9.3, backport this also.