Changes from upstream are limited to change #include paths so that I
can place header files and included "c" files in a subdirectory. I
didn't keep the unit tests from sphlib but instead verified them by
running them manually. I will implement the same tests using the
Pl_SHA2 pipeline except that sphlib's sha2 implementation supports
partial bytes, which I will not exercise in qpdf or our tests.
Jay Berkenbilt