Force TechRacer maps when image map is selected. Fixes
Google Code issue #882
If you start a TechRacer map with an image map selected, the resulting map will likely to be completely unplayable.
So this commit disables this.
City.ogg=HSR ( http://elhombresinremedio.com )
Compost.ogg=HG
EarthRise.ogg=Jonatan Nilsson
oriental.ogg=Jonatan Nilsson
Rock.ogg=HSR ( http://elhombresinremedio.com )
sdmusic.ogg=Kevin MacLeod - "Hitman" [sheepluva edit]
snow.ogg=Jonatan Nilsson