Move declaration of IVideoCapture class into precomp.hpp, make some methods of IVideoCapture pure virtual

Remove implementation of CvCapture interface for Intel PerC camera. Add IVideoCapture interface and implementation of this one for Intel PerC camera

Also deleted miscellaneous remaining multimon cruft.
Deleted #include <winuser.h>, because <windows.h> includes it
already.

This should have a nice side effect of preventing us from
accidentally using any Windows API that's too new.

Set and Get methods are not implemented;
Camera based video capture is broken due to modifications.

TIFF build was fixed;
Direct Show back-end was enabled;
More accurate guards implemented.

GPU module turned off;
TIFF support turned off;
Windows Managment and Video IO (VFW) turned off.

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>

* removed OpenGLFuncTab, now extensions are loaded internally
* added support of GlBuffer and GlTexture2D to InputArray/OutputArray
* added ELEMENT_ARRAY_BUFFER and PIXEL_PACK_BUFFER targets
* added copyFrom/copyTo method for GlBuffer and GlTexture2D
* removed GlFont
* removed pointCloudShow
* removed OpenGLCleanCallback
* added Access parameter to GlBuffer::mapHost
* added autoRelease parameter to all create methods

This reverts commit 2e7656db.

* removed OpenGLFuncTab, now extensions are loaded internally
* renamed GlTexture -> GlTexture2D
* added support of GlBuffer and GlTexture2D to InputArray/OutputArray
* added ELEMENT_ARRAY_BUFFER and PIXEL_PACK_BUFFER targets
* added copyFrom/copyTo method for GlBuffer and GlTexture2D
* removed GlFont
* removed pointCloudShow
* removed OpenGLCleanCallback

added support for Ximea cameras (patch by Marian Zajko), fixed GCC warnings in MOG2 background subtractor.