SVR2 "pr" bug fix

[Doug Gwyn]

As reported (problem id #743) in the UNIX System V Known Problem List,
the command "pr -d -2 -l61" (any odd page length, multi-column output)
results in only one page of output.  Here is what I believe to be a
fix for this bug.

...
char xxxnotused[] = "@(#)pr.c	1.3";
...
nexbuf()
...
		/* DAG -- bug fix (added "+ Dblspace - 1" in the following line) */
		for (j = (Length - Margin + Dblspace - 1)/Dblspace; --j >= 0; ++bline)
...