Add -R as a synonym to -r for rm(1)

Some scripts require this.

rm.1

@@ -3,7 +3,7 @@
 rm \- remove files and directories
 .SH SYNOPSIS
 .B rm
-.RB [ \-fr ]
+.RB [ \-fRr ]
 .RI [ file ...]
 .SH DESCRIPTION
 .B rm
@@ -13,6 +13,9 @@ removes the given files and directories.
 .B \-f
 ignore files that cannot be removed.
 .TP
+.B \-R
+equivalent to -r.
+.TP
 .B \-r
 remove directories recursively.
 .SH SEE ALSO

rm.c

@@ -10,7 +10,7 @@
 static void
 usage(void)
 {
-	eprintf("usage: %s [-fr] FILE...\n", argv0);
+	eprintf("usage: %s [-fRr] FILE...\n", argv0);
 }
 
 int
@@ -20,6 +20,7 @@ main(int argc, char *argv[])
 	case 'f':
 		rm_fflag = true;
 		break;
+	case 'R':
 	case 'r':
 		rm_rflag = true;
 		break;