UI improvements for autosave mode 2 and 3.

Feature request 219  -   Allow Quitting from Battlescape when Autosave=3
http://openxcom.org/bugs/openxcom/issues/219

The battlescape option screen for autosave mode 0 and 1. There are no changes.
![screen018](https://f.cloud.github.com/assets/3616568/1020745/eec8e506-0cc0-11e3-8e6b-266314bae993.png)

Autosave mode 2:
![screen019](https://f.cloud.github.com/assets/3616568/1020746/03441d3e-0cc1-11e3-9332-c852944c4a30.png)
![screen020](https://f.cloud.github.com/assets/3616568/1020748/0b1cb0fc-0cc1-11e3-86c5-849c138a02e0.png)

Autosave mode 3:
![screen021](https://f.cloud.github.com/assets/3616568/1020749/193b9c20-0cc1-11e3-810c-8cced071dd28.png)