* MD5++.cc, MD5++.h: Remove this class.
* csu_util/MD5Sum.cc, csu_util/MD5Sum.h: New more complete MD5 class.
* Makefile.am (setup_SOURCES): Adjust to new files.
* download.cc (validateCachedPackage): Simplify, using the new class.
* install.cc (md5_one): Ditto.
* package_source.h (packagesource::md5): Change to be an object of the
new class.