Fix deinterlace initialization

Without this commit, the deinterlace setting is wrong if the video is
not opened directly with the doc but later.

Fix this situation by always initializing the deinterlace setting when
the doc is opened, not only when the video defined inside the doc is
found.
(PhVideoEngine) Make sure _deinterlace is initialized

On Windows, it was implicitely initialized to true, and this
was causing VideoTest::deinterlaceTest to fail.
Merge pull request #206 from tlecomte/tlDeinterlaceFix

Tl deinterlace fix