Fix for added menus like Wine and Crossover

When determining which extras menus to merge, MATE-menus take the name of the file to determine to directory to look in. Thus, it looks for applications in mate-applications-merged, instead of applications-merged. This is the result:
![matemenu1](https://f.cloud.github.com/assets/1478678/323784/0c3eb4c4-9acc-11e2-8850-792f3e2be693.png)

This fix will make mate-menus look in applications-merged, so the menus are added back again:
![matemenu2](https://f.cloud.github.com/assets/1478678/323785/15de13f8-9acc-11e2-8664-dd583cb0aefb.png)