Clarified floodfill documentation

Clarified what value floodfill sets pixels in the mask to when FOODFILL_MASK_ONLY is set.
Merge branch '2.4'
Redo the Sphinx check to do the same thing on all platforms.

This also fixes the bug where the Sphinx version gets detected as
"Sphinx vX.Y.Z" instead of "X.Y.Z" on Unix-like systems.
fixed compilation errors
Merge pull request #817 from pengx17:2.4_ocl_bitwise_cleanup
Merge pull request #829 from SpecLad:sphinx-ver-1
Merge pull request #831 from jet47:fix-build
removed separate example for reading image sequences and modified starter_video.cpp to better explain the functionality of VideoCapture. I also added a bit more explanation in the documentation of the VideoCapture interface
removed starter_image_sequence.cpp
Merge pull request #828 from tim36272:patch-1
gpucodec module for video decoding/encoding
gpuarithm module for arithmetics operations on matrices
gpufilters module for image filtering
CV_GPU_TEST_MAIN macros
gpunvidia module for NCV & NPP API
removed columnSum function (it is a duplicate for reduce)
added private header to gpunvidia module
replaced NCV_EXPORTS with CV_EXPORTS
made objdetect dependecy for gpunvidia optional
moved rectStdDev to gpuarithm