WIP: basesrc: Add test for duration when doing reverse playback
While cleaning my backlog of branches, I realized that I had written the exact same code as 4a025d77, but with a unit test, so let's merge the unit test to avoid future regressions.
Also implemented minimal reverse playback support in fakesrc to build unit test.
This tests the code added in 4a025d77
Edited by Olivier Crête