ser*.[hc] cleanups

[Andrew Cagney]

FYI,

I've just checked in the first of a number of cleanups to the serial
code.  This round only contained cosmetic changes:

	o	stripped out K&R style declarations

	o	replaced macro's directly calling functions
		with indirect function calls.

Next is to consolidate ser-tcp, ser-unix and ser-pipe so that they are
ready for some async changes that Elena is preparing.

	enjoy,
		Andrew

PS: It got through basic testing, testing continuing....