Make -r mean exactly the same thing as -E for increased compatibility

with GNU sed.

MFC after:	7 days

usr.bin/sed/main.c

@@ -130,8 +130,9 @@ main(int argc, char *argv[])
 	fflag = 0;
 	inplace = NULL;
 
-	while ((c = getopt(argc, argv, "EI:ae:f:i:ln")) != -1)
+	while ((c = getopt(argc, argv, "EI:ae:f:i:lnr")) != -1)
 		switch (c) {
+		case 'r':		/* Gnu sed compat */
 		case 'E':
 			rflags = REG_EXTENDED;
 			break;

usr.bin/sed/sed.1

@@ -39,11 +39,11 @@
 .Nd stream editor
 .Sh SYNOPSIS
 .Nm
-.Op Fl Ealn
+.Op Fl Ealnr
 .Ar command
 .Op Ar
 .Nm
-.Op Fl Ealn
+.Op Fl Ealnr
 .Op Fl e Ar command
 .Op Fl f Ar command_file
 .Op Fl I Ar extension
@@ -144,6 +144,10 @@ all of the commands have been applied to it.
 The
 .Fl n
 option suppresses this behavior.
+.It Fl r
+Same as
+.Fl E 
+for compatibility with GNU sed.
 .El
 .Pp
 The form of a