net/openpgm: fix build with python3
- fix build with python3 (trivial change)
- clarify license (it's LGPL21+) and add LICENSE_FILE
- simplify docs and examples installation
- whitespace fixes
- bump PORTREVISION because default package changed - examples now installed to EXAMPLESDIR instead of EXAMPLESDIR/examples)
Approved by: vg (maintainer)