Add support for WEP-64

Wifi routers still support WEP64.
Include WEP64 support in the headers
and use the `set w k` command for WEP64
rather than `set w p` (for key rather than
passcode)
WEP64 should be set to 8

(typo, should not have been 6, manual says 8)
Merge pull request #1 from polastre/main

Support WEP64