* modules/stream_out/transcode.c: added a floating point "scale" option for video transcoding. When specified, you don't need to specify the width and height of the output video.
 Also changed the width and height options so that if only one of them is specified, the other one is calculated automatically so as to keep the aspect ratio of the video.
* modules/mux/ogg.c: fixed crash when removing streams.
* modules/codec/theora.c: for now the theora encoder requires a width and height which are multiple of 16.