ed(1): Allow the omission of one address in (.,.) and (.;.) address ranges

With this patch, ",n" is an abbreviation for "1,n", ";n" abbreviates
".;n". The "n," and "n;" variants mean "n,n" and "n;n", respectively.
Also, piping to a shell command does not count as a save, so don't reset
the modified flag.

Obtained from: OpenBSD (CVS Rev. 1.58, 1.59)