Wrapping the tiff support library for tcl is a bit more complicated
than libz, or libpng.

(1)	libtiff comes with its own configure command, and there is no
	configure.in. This means that it is not possible to lift the
	relevant sections out of it for the configure of the
	binding.

	Also this configure is not exactly autoconf based (Seems so).
	One of the things it has to be told is the target/build architecture,
	as argument instead of via option. Because of this we cannot use
	AC_CONFIG_SUBDIRS to run the sub-configure.

	We do it directly, and are thus also able to avoid the symlink
	we had to have in libjpeg/tcl.

(2)	The tif sources have usage of tdarg.h hardwired into them.
	This means that a compiler not using this header, but varargs.h
	cannot be used. This is checked in configure.