- update ppport.h and remove the duplicate definitions from

	- update ppport.h and remove the duplicate definitions from
	  Imager.xs.  Had to mangle ppport.h to prevent duplicate global
	  function definitions.
	- newer versions of tifflib require that all of the function
	  pointers passed to TIFFClientOpen be non-NULL, the mmap() and
	  munmap() pointers were always NULL and the sizeproc was
	  sometimes NULL.