pagevideos: Prevent renaming video if file name prefix is already used
This prevents some issues and weirdnesses with losing the video thumbnail, etc.
City.ogg=HSR <http://elhombresinremedio.com>
Compost.ogg=HG
EarthRise.ogg=Jonatan Nilsson
Fruit.ogg=Valentin Kraevskiy
Jungle.ogg=Valentin Kraevskiy
Nature.ogg=John Dum
Pirate.ogg=Jonatan Nilsson
Rock.ogg=HSR <http://elhombresinremedio.com>
olympics_sd.ogg=yd <http://opengameart.org/users/yd>
oriental.ogg=Jonatan Nilsson
sdmusic.ogg=Kevin MacLeod - "Hitman" [sheepluva edit]
snow.ogg=Jonatan Nilsson