replace std::swap with own code

Improve comments to indicate actual usage of WORDS_BIGENDIAN where
it is tested with #ifdef rather than #if

Use correct integer types for arguments to TIFFGetField to avoid corruption
of values and failed loads of TIFF file when using cv::imread().

Added test where both big and little endian TIFF files are read using imread().

Fixed build of 3rdparty libtiff on big endian hosts.

Reduced memory required during decode_tile16384x16384 test by not converting
large grayscale test image to color image during read.

The LLVM/Clang 3.3 has a bug when compile a cl kernel with
assignment of a scalar to a vector data type. This patch
could work around this bug.
Signed-off-by: Zhigang Gong <zhigang.gong@intel.com>

* BruteForceNonLocalMeans
* OpticalFlowBM

* out of border access in edgesHysteresisLocalKernel
* incorrect usage of atomicAdd