Add version specified ports of separated standard Python modules for
non-default Python versions:
- Add pyXY-{sqlite3,gdbm,tkinter} ports for generating binary packages
- Improve/add pkg-message to point users to install respective packages of separated Python standard modules
- Add COMMENT to explicitly show the Python version that package should be used with
- Simplify version-related PYTHON_* for lang/python35
databases/py32-gdbm
databases/py33-gdbm
databases/py34-gdbm
databases/py35-gdbm
databases/py32-sqlite3
databases/py33-sqlite3
databases/py34-sqlite3
databases/py35-sqlite3
x11-toolkits/py32-tkinter
x11-toolkits/py33-tkinter
x11-toolkits/py34-tkinter
x11-toolkits/py35-tkinter