mkindex: ignore leading /, < and . as well

Just as it already ignored leading dashes. This makes it sort
"/etc/host" in E and ".netrc" in N.

mkindex.pl

@@ -129,7 +129,7 @@ sub single {
 sub sorting {
     my ($s) = @_;
     $s = uc($s); # first uppercase
-    $s =~ s/^[-]+//; # remove initial junk
+    $s =~ s/^[-<\/.]+//; # remove initial junk
     return $s;
 }