it wants to store a pointer to itself in an idWinVar - on 32bit idWinInt
was suitable for that, on 64bit it's not, so instead convert the pointer
to a hex-string and stuff it in a idWinStr
also fix a crash when adding a choiceDef in the gui editor
rvGEWindowWrapper is still TODO - it's not as straightforward, because
it insists on storing a pointer in an idWinVar (using idWinInt), but there
is no idWinVar type for pointers
Editor also seems to start, didn't test much further.
Only tested 32bit Windows, I fear the editor code isn't 64bit clean..
I hope I haven't broken anything elsewhere..
