WinCon: define all of PDC_WIDE, UNICODE, _UNICODE if one of those are defined

[GitMensch]

Per MSDN one should always define both macros, as they are used in different contexts, but must match. The definition of UNICODE can also be provided by the build environment, especially with MSVC, in which case PDC_WIDE must be defined as well.

In general - shouldn't we move that to another (common internal) header, wrapping it in #ifdef _WIN32?

Apart from wincon we have that also in wingui, vt and (not sure it is needed/useful there) fb:

https://github.com/Bill-Gray/PDCursesMod/blob/d2f479a8301e0b9b6278a98524efaaaa5e3a1877/wingui/pdcwin.h#L13-L20 https://github.com/Bill-Gray/PDCursesMod/blob/d2f479a8301e0b9b6278a98524efaaaa5e3a1877/vt/pdcvt.h#L9-L16 https://github.com/Bill-Gray/PDCursesMod/blob/d2f479a8301e0b9b6278a98524efaaaa5e3a1877/fb/pdcfb.h#L1-L8