Add a WINEVER environment variable

[Andreas Mohr]

Hi,

I'm afraid I don't like the naming, since it's potentially confusing
(plus, it somewhat goes against established rules, "WINE + function").
What about WINEWINVER instead? I for one like it much more.
Also, this doesn't take into account that we're also able to set the
DOS version. So what would that be called then? WINEVER, too? ;-)
WINEWINVER and WINEDOSVER is a much better choice, IMHO.

Greetings,

Andreas