1) Cameras started with Y16 (V4L2_PIX_FMT_Y16) format via v4l2 backend will now exhibit default camera behavior, i.e. convert the 16-bit image to BGR as with all other formats. 16-bit 1-channel output will now only be produced for Y16 if CV_CAP_PROP_CONVERT_RGB is set to "false" using VideoCap::set method.
2) v4l2 videoio backend now supports setting CV_CAP_PROP_FOURCC explicitly (icvSetPropertyCAM_V4L function in cap_v4l.cpp), allowing users to manually set the codec on cameras that support multiple codecs.

  * __fp16 doesn't exist on nvcc, but it slips through ifdef guard

Fixes clang -Wextra-semi warnings.

* Changes delegate property from assign to weak

In modern Objective-C delegate should be weak. In very rare conditions you might want delegate be strong.
Assign for delegate is sign of legacy code.
This change prevents crash when you forget nil delegate in dealloc and makes rush with nilling delegate unnecessary.
This change shouldn't break any existing code.

* Adds implementation for setters and getters for weak delegate properties for non ARC Obj-C files

For whatever reason compiler can't synthesize these.
And yes, it's time to convert all Objective-C stuff to ARC.

* seriously improved performance of blur function, especially 3x3 and 5x5 cases

* trying to fix warnings and test failures

* replaced #if 0 with #if IPP_DISABLE_BLOCK