This gets FileDialog updated and working on Windows. It also
removes removes the "wx3" build configurations and makes the default
Debug and Release builds wx3-only.
Still need to get VSTs updated.
To test on Windows:
1) Install gstreamer 1.0 devel and runtime
2) Add an GSTREAMER_SDK environment variable which points to the
gstreamer base directory
3) Uncomment USE_GSTREAMER in configwin.h
For Resample.* and QualityPrefs.cpp, this commit has my restructuring for distinguishing constant-rate vs variable-rate resamplers more generally. I think it's complete and ready for const-rate, but I have more review and testing to do for the var-rate cases.
Variable-rate resampling is not implemented here, so Time Tracks are still broken, but this is a milestone in getting to a more general and correct structure.
Also I think this fixes AboutDialog issues Steve noticed.