Fix NoX11 build not showing Preferences Window by including NoX11 into the Target Membership of PreferencesWindow.xib. An error "-[PreferencesWindowController loadWindow]: failed to load window nib file 'PreferencesWindow'" occurs. Reference <http://stackoverflow.com/questions/16838245/cocoa-failed-to-load-window-nib-file-when-nib-is-localized>
Merge pull request #144 from kojiishi/fix-NoX11-build

Fix NoX11 build