Refer to environ(7) for description of COLUMNS instead of describing it

in-line. Document effects of locale environment variables in the same way.

usr.bin/sed/sed.1

@@ -505,18 +505,17 @@ This is the same as specifying the
 option on the command line.
 .El
 .Sh ENVIRONMENT
-The following environment variables affect the execution of
-.Nm :
-.Bl -tag -width ".Ev COLUMNS"
-.It Ev COLUMNS
-If set, specifies the user's preferred output width in column positions.
 The
-.Dq l
-command uses this value to fold long lines to an appropriate width.
-By default,
+.Ev COLUMNS ,
+.Ev LANG ,
+.Ev LC_ALL ,
+.Ev LC_CTYPE
+and
+.Ev LC_COLLATE
+environment variables affect the execution of
 .Nm
-attempts to automatically determine the terminal width.
-.El
+as described in
+.Xr environ 7 .
 .Sh DIAGNOSTICS
 .Ex -std
 .Sh SEE ALSO