Set the SDK to 10.0.17763.
Set a default WXWIN property if the WXWIN environment variable is not set.
Source files will be interpreted as UTF-8 by default.
Use LTCG for release builds.
The project files move from lib-src into the win/Projects folder.
Intermediate files are now kept well away from the files we want.
Less use of '..' and more of $(SolutionPath) in paths.