accept slashes in RandR output names (+test) (Thanks dbp)

fixes #785

testcases/t/196-randr-output-names.t

@@ -0,0 +1,22 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+# Verify that i3 allows strange RandR output names such as DVI-I_1/digital.
+# Ticket: #785
+# Bug still in: 4.2-256-ga007283
+use i3test i3_autostart => 0;
+use File::Temp qw(tempfile);
+
+my ($fh, $filename) = tempfile(UNLINK => 1);
+print $fh <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+workspace 2 output DVI-I_1/digital
+EOT
+
+my $output = qx(../i3 -C -c $filename);
+unlike($output, qr/ERROR/, 'no errors in i3 -C');
+
+close($fh);
+
+done_testing;