* Initialize SDL before opening the SDL audio output.
  * Prevent two SDL video outputs or audio outputs to be spawned at the
    same time to avoid ugly crashes.
  * The SDL plugin now says whether we are using software or hardware YUV
    in its window title.
  * We now stop at the first ':' when looking for a module name, to easily
    pass information to the modules. Possible example: --vout sdl:software,
    implementation of such an option is left as an exercise.
  * Merged filter_bob and filter_bob422 into filter_bob. Use --filter bob
    to deinterlace 422 into 420 as well.
  * Factorized code common to most filters and the video output, optimized
    a few filters by aligning data and reading 64 bits at a time.
  * Two new absolutely useless, CPU-eating, resource-wasting, but fun
    filters: enjoy `transform', which performs flips and 90� rotations, and
    `distort', which performs animated image effects (currently only a naive
    sine wave is implemented). Usage examples:
       --filter transform:hflip
       --filter transform:vflip
       --filter transform:90
       --filter transform:180
       --filter transform:270
       --filter distort:wave