correct Research Unix edition "appeared in" use in HISTORY

Starting from "Combined Table of Contents" in Doug McIlroy's
"A Research UNIX Reader" a table of which edition manuals appeared in.
Checked against manuals from bitsavers/TUHS and source from TUHS where
available.
Ingo points out there are cases where something is included but not
documented until a later release.
bcd(6)		v6	v7
printf(3)	v2	v4
abort(3)	v5	v6
system(3)	v6	v7
fmod(3)		v5	v6
ok schwarze@

src/lib/libc/stdlib/qsort.3

@@ -29,9 +29,9 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	$OpenBSD: qsort.3,v 1.26 2019/05/15 16:58:56 schwarze Exp $
+.\"	$OpenBSD: qsort.3,v 1.27 2020/02/08 01:09:57 jsg Exp $
 .\"
-.Dd $Mdocdate: May 15 2019 $
+.Dd $Mdocdate: February 8 2020 $
 .Dt QSORT 3
 .Os
 .Sh NAME
@@ -273,4 +273,4 @@ function conforms to
 A
 .Fn qsort
 function first appeared in
-.At v3 .
+.At v2 .