workaround cmake 2.8.10 not allowing CTEST_CUSTOM_POST_TEST arguments
improve Xvfb handling when ctest is cancelled partway through
fix bug in test_pretty_print.cc / Cmakefile

The build needs to be after Python binary has been found because the Python
binary path is passed to the .cc compile through a -D flag.
Merge branch 'master' of github.com:openscad/openscad into cmake_workaround

Conflicts:
	tests/virtualfb.sh
Merge pull request #271 from openscad/cmake_workaround

Cmake workaround