When we call gst_buffer_pool_set_config() the pool may return FALSE and
slightly change the parameters. This helper is useful to do the minial required
validation before accepting the modified configuration.
https://bugzilla.gnome.org/show_bug.cgi?id=727916
If a pool config is being configured again, check if the configuration have changed.
If not, skip that step. Finally, if the pool is active, try deactivating it.
https://bugzilla.gnome.org/show_bug.cgi?id=728268
Tag allocated buffers with TAG_MEMORY. When they are released later,
only add them back to the pool if the tag is still there and the memory
has not been changed, otherwise throw the buffer away.
Add unit test to check various scenarios.
Fixes https://bugzilla.gnome.org/show_bug.cgi?id=724481