Register AudioDub as a NICE filter.
Register Splice as a NICE filter.
Fix corrupted AviSource output due to wrong frame pitch. Closes bug #36.
Overlay: fix crash on mask and some memory leak.
Merge pull request #39 from innocenat/overlay-fix

Overlay: fix crash on mask and some memory leak.
Clamp frame index to valid range in Cache. Partially fixes #38.