poll: improve debug

So that we can see the return values of functions in the log.
pluginloader: check read/write before closed

first try to read or write on the socket before checking the closed state. This
makes sure we handle all data on the socket before erroring out.
gst-launch: exit with an error code when an error occured

If the pipeline failed to pre-roll or the user interrupted the
execution then set the exit code to a positive value.

https://bugzilla.gnome.org/show_bug.cgi?id=712300
query: Fix gi annotations of gst_structure_new_custom()
gstutils: Escape stream id format in comments

These must be escaped for gtk-doc to parse the comments without warnings.

https://bugzilla.gnome.org/show_bug.cgi?id=714989
ghostpad: copy sticky events to SRC ghostpads

Update the sticky events on SRC ghostpads when retargeting. This ensures
that the ghostpad has the exect same sticky events as the target pad. We
don't want to do this for SINK ghostpads, they got the events from
downstream and we don't want to overwrite them with the target pad
events.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=707621
baseparse: ensure to preserve upstream timestamps

... rather than have subclass coming up with an internally parsed one.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=707230
bin: Resync iterator if necessary