macosx: Use input_ItemHasErrorWhenReading to display a small icon if there was an error when reading. This allow us not to display the message panel each time we have an error when reading.

Regarding the new look, feel free to improve.

Using the registry when we can avoid it is a wrong idea, IMHO.
Easier to delete when you delete %appdata%/vlc

Sorry, I don't liked this 'feature'

Delete the "QPainter::begin: A paint device can only be painted by one painter at a time" boring messages in playlist.

This commit build compilation on window.

This reverts commit d632ffe1.