Fix reading of 16-bit TIFF images on big endian host.

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.