Older versions of the server default to 8bpp, which breaks some of our
tests (admittedly, this shouldn't be the case, but it's probably better
to test in the same configuration as is used by 99.99% of the users
rather than adjusting or disabling tests in the remaining 0.01%).
The tests are known to fail for the other tested ports, so don't enable
them for now.
Also, using a special environment variable allows to detect when the
test is being run under Xvfb, which behaves differently from the normal
X server in some cases.
Add CMake-based build system.
Merge the original branch without any changes except for resolving the
conflict due to moving the contents of .travis.yml to a separate file by
propagating the changes done in this file since then to the new script
and rerunning ./build/update-setup-h and ./build/cmake/update_files.py
to update the file lists changed in the meanwhile.
Closes https://github.com/wxWidgets/wxWidgets/pull/330
