decodebin2: activate ghost pad before targetting

Activate the decodebin2 pad before setting the target. This makes sure
that the events are copied.
tcp: fix compilation with MSVC

error C2440 at line 165 of gsttcpserversink.c
type cast error: cannot convert from GSocket* to GstMultiSinkHandle
theoraparse: Fix event handling

Send CAPS event before any SEGMENT events or any other events
that must come in order after the CAPS event.
uridecodebin: copy sticky events
decodebin2: copy sticky events
audiodecoder: use segment start as fallback ts if no other available

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=709965
audiodecoder: no fallback to segment start for reverse playback

See https://bugzilla.gnome.org/show_bug.cgi?id=709965