fwknop-2.6.4

updates fwknop to v2.6.4; built/tested on OS X Yosemite (10.10).

[CHANGELOG](https://github.com/mrash/fwknop/blob/ecf00d36bdaf94196a454bea1225dfa0827f936b/ChangeLog)
fwknop: update 2.6.4 bottle.