gmtime_s() usage incompatible with C standard
This change to date.c uses gmtime_s() according to the Microsoft CRT, which is incompatible with the C standard since it has reversed parameter order as well as a different return type.
Hence the following lines do not work on Windows if not compiled with MS VC:
- https://gitlab.gnome.org/GNOME/libxslt/-/blob/master/libexslt/date.c#L696
- https://gitlab.gnome.org/GNOME/libxslt/-/blob/master/libexslt/date.c#L738
OpenSSL implements a workaround for this issue by testing explicitly for the _MSC_VER
macro. Maybe something similar could be used in libxslt as well?