fix warnings about missing destructors in FeatureDetector and DescriptorExtractor classes and their derivatives

Fixed CMake cached variables

 "error: explicit template specialization cannot have a storage class"

- Save current screen (CTRL+S), with png, jpg, jpeg, bmp format support
- OpenGL rendering enable (make Qt very fast)
      -> working on opengl callback (done soon)
- Rendering optimised (with and without openGL)

Corrected Mask operator (from documentation mask must be a char matrix with non-zero values in the region of interest)

Commenting out CV_CameraCalibrationBadArgTest because a crash in its constructor prevents opencv_test to run anything

- fixed bug ticket #412

- save/load window parameters implemented !

fixed the output disparity at the extreme cases (minDisparity or minDisparity + numOfDisp - 1). Thanks to Patrick Mihelich for the report (trac #395)

- imgregion shortcut implemented (CTRL+O)

- imgregion (as with Matlab) implemented

- aspectRatio is controled by cvSet/getWindowProperty

- fix CMake OpenGL compilation

- fix zoom offset of 0.5
- fix CMake problem with QT detection
- Code optimisation

Adapted mtu and packed size
Some minor fixes in gstreamer because not implemented support of v4l v4l2 in the wrapper
default beahvior must be v4l v4l2 or libv4l backends