Combine all the different configurations together so the project files
are more generic and maintainable.
Also standardise the layout so all the project files will be similar and
all have the same standard elements (even if empty).
Add 64-bit configurations.
Additional specifics:
wxWidgets: Common stuff into the property sheets.
pthreads: Fixes the LNK4068 warning.
portaudio: Devel config added.
libjpeg: Non-existent file removed.
Side note: libjpeg is barely used - wxWidgets uses it but doesn't have
to, ZeroGS uses it but we don't develop that anymore.
This puts the wxWidgets3.0 and libpng generated library files into the
deps folder, and puts the other builds files in a subdirectory from
where the project files are located. This is consistent with all the
other 3rdparty projects.
The output libraries for Devel builds are also suffixed with -dev
instead of -dbg now.
This configure the VS2013 files so that the now external libpng and
libjpeg libraries are used, and to place some of the common stuff into a
property sheet.
For deleted files, I've chosen to exclude from build instead of removing
them from the project file. It's less work to re-add them if they're
required at a later stage.
kojin