X11 headers and libraries are only required if we're actually using X11
which may not be the case.
This allows to build wxGTK on the systems using Wayland-only GTK.
uuid should be linked before oleacc, otherwise it causes multiple definition of `IID_IAccessible' (with MinGW64 gcc).
To simplify even more, specify all required libraries in wxTOOLKIT_LIBRARIES, in the same order as in the makefiles.
Add uxtheme library, it is required since wxUxThemeEngine wrapper has been removed.
Add CMake build system for libraries, tests and samples
update_files.py converts build/files into CMake format.
build/update-setup-h has been modified to update build/cmake/setup.h.in.