Cocoa: avoid displaying window when command-line contains '-h' or '-help'

There was already a check in place to avoid displaying a window
in certain modes such as vnc, nographic or curses.

Add a check for '-h' and '-help' to avoid displaying a window for a split-
second before showing the usage information.

Signed-off-by: Alexandre Raymond <cerbere@gmail.com>
Signed-off-by: Andreas Färber <andreas.faerber@web.de>

ui/cocoa.m

diff --git a/ui/cocoa.m b/ui/cocoa.m
index 1ff1ac6..e1312d3 100644
--- a/ui/cocoa.m
+++ b/ui/cocoa.m
@@ -872,7 +872,8 @@
             if (opt[1] == '-') {
                 opt++;
             }
-            if (!strcmp(opt, "-vnc") ||
+            if (!strcmp(opt, "-h") || !strcmp(opt, "-help") ||
+                !strcmp(opt, "-vnc") ||
                 !strcmp(opt, "-nographic") ||
                 !strcmp(opt, "-version") ||
                 !strcmp(opt, "-curses")) {