Replaces `NXDK` ifdefs that relate to the lack of wchar APIs
with the more general `DEVILUTIONX_WINDOWS_NO_WCHAR` ifdefs.
This should make it much easier to port to Windows 98.
Reduces the size of the `PathNodes` array from 28 KiB to just 8 KiB.
Also reduces the size of `pnode_tblptr` from `300 * sizeof(void *)` to
`300 * 2` bytes.
The C++ `std::locale("")` constructor performs a static
initialization of all the facets on the first call.
For example, this includes things like currency formatting.
Avoid all of that by using the environment variables with a fallback to
the equivalent C locale call.
Gleb Mazovetskiy
Andrew James
John Törnblom