Add a test to verify that stats about sent and received packets are
correct even when using buffer lists.
NOTE: the newly introduced get_session_source_stats() selects the
desired source (sender or receiver) by filtering them by type (using the
get_sender parameter) rather than by ssrc because this simplifies the
code and it's good enough for testing purposes as there is usually one
source per type in the test setup.
Filtering by ssrc would have required handling asynchronous signals like
"on-new-sender-ssrc", with the relative locking, just to retrieve the
actual ssrc of the sender.
The tests create a buffer list and then use the chain_list callback to
verify that the correct packets have been pushed.
Move the creation and validation code next to each other so that the
reader can more easily understand what is going on.
While at it add some comments to introduce the two related functions.
Make it possible to differentiate between the position in the list and
the packet index in the global structures in check_packet, in some
future case the list may change, in case some element removes a buffer
from the list, and the two indices may not coincide.
Port the rtpbin_buffer_list test to GStreamer 1.0 and re-enable it.
Some other changes include:
- the check on the caps has been moved from the buffer level to the
pad level;
- remove underscore prefix from static functions names, this is not
idiomatic in C and rarely used in the other tests;
- the unused header_buffer variable has been removed;
- check_group() has been renamed to check_packet() because in
GStreamer 1.0 there is no concept of "group" anymore, the comments
have also been updated to reflect this.
