pc/devlpt.c		1991/1204		Created.
		1992/0111
		1992/0114
		1992/0205
		1992/0321
		1992/0711
		1993/0224		Bug fix?: delay setvec to attach time.
		1994/0324		New interrupt interface. Bug fix?: swap lpt1, lpt2.
		1994/0331		Loop a bit waiting for printer before going to sleep.
		1994/0513		Bug fix: turn off interrupts until we want them.
		1995/0108		Add lptbread, lptbwrite.
		1995/0726		Anonymize lptcreate.
		1997/0327		Clean up driver. No bug fixes.
		1997/0408		Add devchar and name to Dev structure.
		1998/0319		Change dev read and write to use vlong offset. Formatting edits.
		1998/0825		Bug fix: print format.
		1998/0910		Change VectorLPT to IrqLPT.
		1999/0714		Use ioalloc.
		1999/0819		Add name to intrenable call.
		1999/1230		Handle DEVDOTDOT. (Big bug fix.)
		2000/0813		Bug fix: only error out if Fpe is not set.
		2001/0413		Handle ECP parallel ports.
		2001/0527		Convert to 9P2000.
		2002/0109		Add devshutdown.