CvCaptureFile::grabFrame() always returns 1 regardless, which causes
dead loop when relying on the return value of VideoCapture::read().

- changing license header
- fixed bug in QtKit when changing camera resolution

OpenCV's automatic builds don't care if you store an unsigned int into
an int, but they don't want you to compare signed with unsigned. Does
that make sense?

cap_qtkit does not work when the capture is run outside of the main
thread.
If the capture is launched in a separate thread, then [NSRunLoop
currentRunLoop] is not the same as in the main thread, and has no timer.
see
https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/F
oundation/Classes/nsrunloop_Class/Reference/Reference.html
"If no input sources or timers are attached to the run loop, this
method exits immediately"

Using usleep() (which I previously proposed, and was reverted) is not a
good alternative, because it may block the GUI.

Here is the new proposed solution:
- create a dummy timer so that runUntilDate does not exit immediately
- simplify the loop by using runUntilDate instead of runMode:beforeDate
- fix potential memory leaks (pointed out by Xcode's static analysis)
- fix init to follow Objective-C guidelines
- fax warnings about conversions from size_t to int

[NSRunLoop currentRunLoop] is not the same as in the main thread.
see
https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/F
oundation/Classes/nsrunloop_Class/Reference/Reference.html
"If no input sources or timers are attached to the run loop, this
method exits immediately"

The old code caused grabFrame() to return immediately if the capture
was not done in the main thread.
This code works correctly, even in secondary threads, provided that all
capture functions are called in the *same* thread

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

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

Made all STL usages explicit to be able automatically find all usages of
particular class or function.

reverted the original VideoCapture::read() code; moved frame index check to where it should belong: ffmpeg wrapper; applied patch by Rob Reilink (ticket #1971)