Remove support for the IPX and NCP protocols, and for NWFS.

This was on the list for a longer time now. FreeBSD removed it
recently, too. Their commit msg has some more info:

"IPX was a network transport protocol in Novell's NetWare network
 operating system from late 80s and then 90s. The NetWare itself
 switched to TCP/IP as default transport in 1998. Later, in this
 century the Novell Open Enterprise Server became successor of
 Novell NetWare. The last release that claimed to still support
 IPX was OES 2 in 2007. Routing equipment vendors (e.g. Cisco)
 discontinued support for IPX in 2011."

The commit removes support for NCP (NetWare Core Protocol) and
NWFS (NetWare File System) along with it (both gone from FreeBSD
too since a while).