Change the mac creator type on firebird to MOZB (b is for browser) to avoid

using the same type as Mozilla (MOZZ). This makes url delegation between thunderbird
and firebird work on the mac without the two tripping over each other.

a=brendan on the new creator name

(I forgot to check this change in back in November when I changed browser\app\Makefile.in

browser/app/macbuild/Contents/Info.plist.in

@@ -84,7 +84,7 @@
 	<key>CFBundleShortVersionString</key>
 	<string>@BROWSER_VERSION@</string>
 	<key>CFBundleSignature</key>
-	<string>MOZZ</string>
+	<string>MOZB</string>
 	<key>CFBundleURLTypes</key>
 	<array>
 		<dict>