Reorder tests to not use the same number (#2947)

Distinct numbers make re-running individual tests easier by helping with
tab-completion.

Completeness verified using:
% for i in $(seq 0 600)
do
  files=$(ls testcases/t/$(printf "%03d" $i)-*.t 2>&- | wc -l)
  [ "$files" != "0" ] && [ "$files" != "1" ] && echo "clash: $i"
done

testcases/t/275-ipc-window-close.t

@@ -0,0 +1,52 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • http://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • http://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • http://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Tests that the ipc close event works properly
+#
+# Bug still in: 4.8-7-gf4a8253
+use i3test;
+
+my $i3 = i3(get_socket_path());
+$i3->connect()->recv;
+
+my $cv;
+my $t;
+
+sub reset_test {
+    $cv = AE::cv;
+    $t = AE::timer(0.5, 0, sub { $cv->send(0); });
+}
+
+reset_test;
+
+$i3->subscribe({
+        window => sub {
+            my ($e) = @_;
+            if ($e->{change} eq 'close') {
+                $cv->send($e->{container});
+            }
+        },
+    })->recv;
+
+my $window = open_window;
+
+cmd 'kill';
+my $con = $cv->recv;
+
+ok($con, 'closing a window should send the window::close event');
+is($con->{window}, $window->{id}, 'the event should contain information about the window');
+
+done_testing;