This fixes several crashes with the new tstripdata_start/endstill.
dupli_seq was cleaned up as well as add_scene_strip (moved to a
seperate function)
New features:
* opacity can be used in replace blend mode
* the scene within in a scene track can be changed now within the panel
Also:
* [#7842] Note: setCodec in FormatTab disappeared...
should be fixed by this. (Not a big change, so I just commit and see :)
http://peter.schlaile.de/blender/sequencer/codec_buttons.diff