devel/flatzebra: Update to 0.2.0 + update deps
Update devel/flatzebra and dependent ports.
Also, do a bit of cleanup:
- Remove LOCAL from MASTER_SITES
- Homogenize WWW URLs
- Fix licence (GPLv2+ instead of GPLv2)
- Specify LICENSE_FILE
- Switch to more recent (default) CXXSTD
- Remove useless GNU_CONFIGURE_MANPREFIX