Avoiding mono download prompt

The latest wine from git now prompts not only for Gecko download,
but also for Mono download.

http://winetricks.googlecode.com/svn/trunk/src/install-gecko.sh is
a handy script that I've used for a long time to avoid those pesky
download prompts.  It now also installs mono to avoid that second prompt.

It should be probably be called wine-install-addons.sh now, maybe
I'll rename it that soon.  If you have a better idea for the name,
let me know.

(I've also deprecated the copy that was in winezeug; that one now just 
tells users to get it from the winetricks repo.)