taglib: warn the user when the embedded image is invalid (i.e. was embedded by a broken version of iTunes)

Don't use strerror()
The error message displayed can be useful to debugging purposes.

taglib: Supports in ogg/vorbis base64 encoded embedded album art with COVERARTMIME & COVERART comments.
    Use TagLib namespace for better code readability.

demuxers: Adds attachments support for ogg.
    Fix potential memleaks.

notify: unref the notification popup after we have finished using it. fix a big memory leak, and potential crashes.

control/media_instance.c: Fix a segfault caused by libvlc_media_instance_release. (Patch by Enrique Osuna).

  Someone should check if we could make xtag not send ENDELEM for self-closing tags, as libxml doesn't.

(libmpeg2/xvmc pending)

decoder block_t date to a display date (identify for now)

 - Remove configurable boundary that had never been working anyway (did not match the original value from MUX_GET_MIME)