Starting from now we will not claim that we support GnlObject that have
several source pads as this is
1- Not true at all;
2- the design of priorities in the GnlComposition tree does not allow that;
3- Not very useful in most of the cases and it complexifies quite a lot the code
in the composition.
Conflicts:
configure.ac
tests/check/Makefile.am
This causes races when seeking, reverting for now even if we will
probably want to bring something like that back.
This reverts commit 3549e745a8f0de3977b83c60e9b447afaf55d8a0.
