BUG: Add support for system libtiff 4.0.0-4.0.2

This patch provides a work around for using a system libtiff for
version 4.0.0-4.0.2. The TIFFField data structure was made opaque, but
the necessary methods to access the member to inspect the tiff fields
were only made available in 4.0.3. This patch inspects the headers for
this case, and provides a copy of the declaration for the internal
structure defined in tif_dir.h for uniform access.

Change-Id: I636b7322f02c99b463db83abac6b6f52c4b9dfb3
Merge topic 'UseSytemTiff4.0.2'

dd5a6c3f BUG: Add support for system libtiff 4.0.0-4.0.2
WIP: add relaxation factor

Change-Id: Ia4ba65742b8acf91f50f81a60754e9894e008bbc