avcodec: set absolute/ephemer comments/values correctly
transcode: give proper src fmt for subtitle overlay
livehttp: add DISCONTINUITY on playlist if we have restarted stream

If provided initial-segment-number option, signal discontinuity so
player knows to reset timestamps etc for new segments.
livehttp: don't remove previous playlist on open if segment-number is given

If we provide initial segment-number, most likely we want to continue
where we have left of, so leave old playlist-file there and just
overwrite it when we updated it.

default initial-segment-number is 1 so don't test against 0
wip
debuging...
services_discovery: add SD_CMD_BROWSE
lib: change libvlc_media_discoverer_t creation

libvlc_media_discoverer_new_from_name was creating a services_discovery_t and
was starting it, so libvlc_MediaDiscovererStarted event (or any other events)
could not be received.

To fix that, Split libvlc_media_discoverer_new_from_name into
libvlc_media_discoverer_new and libvlc_media_discoverer_start. That way, we can
attach events between create and start.

libvlc_media_discoverer_new_from_name is now deprecated, but it still works
like before.
lib: add libvlc_media_discoverer_browse

Discover media on a specified uri.
lib: add new libvlc_MediaDiscoverer events

Notify event listener when new items are added or removed.
dsm: refactor

Move browser.c to common.c. This new file contains common browsing functions
that can be used from an access_t or from a services_discovery_t.
dsm: only one function to browse share and directory
dsm: add "smb://" if not present
dsm/sd: discover in a separate thread and handle commands
dsm: don't use netbios struct members directly
dsm: use NETBIOS_FILESERVER define