The third bug-fix release of the v2.2 LTS series

In addition to documentation and example fixes this release
fixes several critical bugs:

- Fix import failure on BSD systems
- Fix import errors in Qt shims for PyQt5 5.11 and PyQt4 4.12
- Fix import errors if bz2 module is not in standard library
- Fix overflow in _path.h
- Fix infinite recursion in transform repr
- Fix bug with XKCD style
- Remove unsafe usage of Popen