Win64 keyword?

[Austin English]

Howdy,

Seems quite a few bugs have been filed recently about our win64
support. While setting the hardware to PC-X86-64 describes the
hardware accurately, it doesn't really tell us if the user is running
32 bit wine or 64 bit wine on their 64 bit OS.

We've already got a win16 keyword, so how about a win64 keyword to
make searching for these bugs easier?

-- 
-Austin