image before sending it to the mosaic.
                    - Add option ("chroma") to force the image chroma
                    - Remove alpha mask code
 * mosaic.c: - Remove bluescreen code
             - Misc cosmetics changes
 * bluescreen.c: New bluescreen filter (mostly cut & paste from mosaic.c)
 * alphamask.c: New alpha mask filter (mostly cut & paste from mosaic_bridge.c)
 * invert.c: don't invert the alpha plane for YUVA images (We also need to
             prevent that for RGBA images ... but that's not really used
             currently)
 * configure.ac, video_filter/Modules.am: add alphamask and bluescreen

 * Add missing space in help string.

 - Remove GNU/makeisms
 - Cleanup

 - Make the desktop icon execute vlc instead of wxvlc

(which is always)

This is not strictly required, but helps propage fix for #1086.

 - Remove net_ListenSingle from LibVLC API
 - Improve error message when network protocol to be used is ambiguous