Reverts [24530] & [24531] (preprocessing related) , add $(DEFS) (-DHAVE_CONFIG_H) to moc command line

Qt4 - Basic implementation of the extensions. Seem to work :D Just .avi now, because we have no good list of extensions in the source code... :D
Ref #763

Qt4 - Fix Compilation on CYGWin. This is a quick fix but not a solution. Again, MOC isn't given HAVE_CONFIG_H so it can't understand ENABLE_VLM or ENABLE_UPDATE. MOCFLAGs would fix that ?

Small fix for Windows compilation... gruiking because MOC doesn't understand #ifdef WIN32... Necessary to add a MOCFLAGS in configure.ac ?

Missing some cases that I could not test.
Also ffmpeg/chroma.c is locked, so I can but leave it broken.
Fix is for the remaining modules is obvious and the issue is easy to detect.

Qt4 - Put the dialog you are not likely to use during playback as QDialogs, meaning centered on MainInterface.
VLM, Preferences, Errors, Podcast_Conf, GotoTime, Help.

- Click on a point on the timeline goes to that point directly
- Draging the timeline makes the position follow your draging
- Hovering a point on the timeline gives you the time of the position under your cursor.

This make break your neck, and kill your favourite ant, but I think this is not that wrong.