Error compiling 199.24 for windows

[Greg Pettyjohn <GregP@bsquare.com>]

Tried to compile for windows and got an error.

The identifier wxAPP_CLASS was not defined in wx_medad.cxx
The offending line number was: 262

I was able to work around this problem by making the following replacement:

//    wxGetResource(wxAPP_CLASS, "wheelStep", &default_wheel_amt);
	      wxGetResource(wxTheApp->wx_class, "wheelStep",
&default_wheel_amt);


Note, the commented-out line was the original source line,
the line directly below is what I added in it's place.

After making this change, it compiles just fine.