Document the input line length limit.

Submitted by:	Dominic Fandrey (original version)

usr.bin/rs/rs.1

@@ -28,7 +28,7 @@
 .\"	@(#)rs.1	8.2 (Berkeley) 12/30/93
 .\" $FreeBSD$
 .\"
-.Dd July 30, 2004
+.Dd February 25, 2011
 .Dt RS 1
 .Os
 .Sh NAME
@@ -237,4 +237,9 @@ Re-ordering of columns is not yet possible.
 There are too many options.
 .It
 Multibyte characters are not recognized.
+.It
+Lines longer than
+.Dv LINE_MAX
+(2048) bytes are not processed and result in immediate termination of
+.Nm .
 .El