aggregator: fix locking

We would unlock a mutex we never locked on SEGMENT
events.
videoaggregator: fix broken locking in update_src_caps function

We would unlock an already-unlocked mutex that we never re-locked.

https://bugzilla.gnome.org/show_bug.cgi?id=732750
videoaggregator: Fix some more the locking logic in update_src_caps

We need the GST_OBJECT_LOCK only to iterate the sinkpads, nothing else.

https://bugzilla.gnome.org/show_bug.cgi?id=732750
mpegts: fix leak of language code
mpegts: atsc: fix leak of short name
mpegts: Add padding to public structures

Allows use to add API in the future without breaking ABI. We broke the API/ABI
once between 1.2 and 1.4, let's try to avoid this in the future even if this
is an unstable library.

https://bugzilla.gnome.org/show_bug.cgi?id=730914
mpegts: fix annotation

https://bugzilla.gnome.org/show_bug.cgi?id=730914
mpegts: docs: add missed *_free methods

https://bugzilla.gnome.org/show_bug.cgi?id=730914
mpegts: use getter for egde linkage descriptor type

https://bugzilla.gnome.org/show_bug.cgi?id=730914
mpegts: Fix dvb linkage leaks

CID #1224130
mpegts: Don't confuse slice allocator with regular one

Previously selector_bytes and private_data_bytes were sometimes allocated and
free using the normal allocator and sometimes using the slice allocator.
Additionally prefer g_strdup() to g_memdup() for strings.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=732789
mpegts: No need to check for NULL before calling g_free()

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=732789
glimagesink: Keep aspect ratio by default

The expected default behaviour for video sink is to maintain the
aspect ratio. Fix the default value to reflect this. The property
default was already TRUE, but the value was not initially TRUE.