Find TIFF library

Find the native TIFF includes and library This module defines

TIFF_INCLUDE_DIR, where to find tiff.h, etc.
TIFF_LIBRARIES, libraries to link against to use TIFF.
TIFF_FOUND, If false, do not try to use TIFF.

also defined, but not for general use are

TIFF_LIBRARY, where to find the TIFF library.