Log Message:
graphics/camlimages: Fix tiff-4.0 regression

When tiff was upgraded to 4.0, camlimages stopped building.  Both
caml and tiff redefine several common typedefs such as uint32.  Unlike
the 3-series of tiff, tiff-4.0 also redefined int64 and uint64.  The
existing hack didn't foresee int64 and uint64 getting used, and so
camlimages broke.

One patch was created and another revised to override the caml typedef
definitions with macros before tiff.h is included.  The original
tiffread.c patch was reworked to override uint16 and uint32 *again*
after the tiff.h include and not before as it was originally.  Very ugly
all around, but I just extended what camlimages was already doing.