gtags_multiwindow_browsing gets put in ftplugin, should be in plugin

[cheater00 cheater00]

As the title suggests.

This is a branch of gtags.vim which correctly gets put in plugin, which again supports the fact that gtags_multiwindow_browsing should be in plugin.

gtags_multiwindow_browsing does not work when it's in ftplugin, it works when it's in plugin.

[marco-oweber]

fixed, thanks