Document that REQUIRES, PROVIDES and KEYWORDS are alos accepted. This

chnage is different to the one suggested in the PR to try to avoid
cluttering the man page too much.

PR:		docs/154494
Submitted by:	kilian <kilian.klimek googlemail.com>
MFC after:	1 week

sbin/rcorder/rcorder.8

@@ -89,6 +89,12 @@ and
 lines may appear, but all such lines must appear in a sequence without
 any intervening lines, as once a line that does not follow the format
 is reached, parsing stops.
+Note that for historical reasons,
+.Dq Li REQUIRES ,
+.Dq Li PROVIDES ,
+and
+.Dq Li KEYWORDS
+are also accepted in addition to the above.
 .Pp
 The options are as follows:
 .Bl -tag -width indent