mpegvideoparse: don't announce incomplete source caps

Don't send any source caps yet if we're still in
drop-buffers-until-we-get-a-sequence-header mode.

Fixes transmuxing of many MPEG-TS/PS streams into
formats which require things like width, height or
codec_data on the input caps.

Also fixes issues when using playbin with decoder
sinks that want width/height etc.

https://bugzilla.gnome.org/show_bug.cgi?id=695879
ladspa: improved port to gstreamer 1.0

Fixes: #698927
mpegvideoparse: don't compare buffer size when checking whether to update caps

https://bugzilla.gnome.org/show_bug.cgi?id=699398
ladspa: Add $(GMODULE_NO_EXPORT_LIBS) for gmodule
ladspa: sync controlled parames in filters and sinks
mpegvideometa: Fix typo in comment

https://bugzilla.gnome.org/show_bug.cgi?id=699827
mpegtsmux: Fix memory leak when using prepare_func

prepare_func will allocate a new buffer to replace the original
one. Instead of using gst_buffer_replace (which causes an extra
refcount increment on the new buffer), we just unref the original
buffer.

https://bugzilla.gnome.org/show_bug.cgi?id=699786
uridownloader: refactor gsturidownloader to its own lib

gsturidownloader can be reused by other plugins, better have it
into its own lib
uridownloader: make cancelled state 'permanent' until a reset

When downloading and cancelling quickly the uridownloader object and the
element using it could miss the cancelled window and the uridownloader
would fetch the wrong URI and block on subsequent fetches.

This was also problematic when stopping elements, while one task would
call the cancel, another element thread could issue a new fetch_uri. As
the cancel state isn't 'permanent' this fetch_uri would block and
prevent the whole element from stopping and going to NULL.

This patch makes the 'cancelled' state permanent until a
gst_uri_downloader_reset is called. This way the element knows the
window where the uridownloader isn't active and only reactivate it when
ready.
uridownloader: properly unref the urisrc between downloads

This prevents leaking the element. Also sets the bus to flushing
to completely reset the downloader state
uridownloader: unlock mutex when switching urisrc state to NULL to avoid deadlock

When chain method was called after gst_uri_downloader_stop and before state has been changed to NULL, execution was blocking on g_mutex_lock.

Conflicts:
	gst-libs/gst/uridownloader/gsturidownloader.c
smoothstreaming: build directory stubs for new plugin

Initial build structure for MS' Smooth Streaming plugin

Conflicts:
	ext/Makefile.am
smoothstreaming: stubs for mssdemux

Just the stubs for mssdemux element.
Also add some useful code from hlsdemux that we intend to reuse
mssdemux: add manifest parsing

Continued implementing:
1) parse the manifest with libxml2
2) detect stream types
mssdemux: pad exposing initial implementation

Does some basic parsing of the stream caps and adds a pad for
each stream detected in the manifest
mssdemux: more manifest parsing and helper functions

Now the mss manifest is able to generate the files urls
mssdemux: initial implementation of the pad loop

The loop will fetch a new fragment and push on its srcpad. Each
stream has its own loop
smoothstreaming: refactor structure names and implement url fetching

Use shorter names for the MSS manifest helper structure and functions.

Also continues the implementation of the stream fetching and pushing loop.
Now it uses the base url correctly and already fetches and pushes the fragments
downstream
mssdemux: mssmanifest: prevent accessing null stream fragment

Move the access to the stream fragment data after the check
if the fragment exists to prevent a segfault
mssdemux: adds mininum error handling

This should care for basic scenarios of errors and EOS to allow
the pipeline to stop correctly