missing .h files

[Steven Schultz]

	Quite a while back, one of the missing include files (mbuf.h)
	was posted to this newsgroup along with an offer to post the
	other missing .h files if the names were specified.

	The other missing .h files are:

		protosw.h
		socket.h
		socketvar.h
		ubavar.h

	Thanks in advance!