[geometry] Fix make_qbk.py to handle empty string returned by os.path.dirname() if called as: $ python /path/to/make_qbk.py. Print current working directory, for easier debugging.

[SVN r86752]
[geometry] Remove building of src/examples from this Jamfile.v2, build only documentation. The src/examples are built by in /libs/geometry/Jamfile.v2.

[SVN r86753]