platforms with a 64-bit long.

The Alpha/Tru64 test problem is a problem in either tarfile or test_tarfile,
not zlib.

crc32 and adler32 return 32-bit values.  by using a long thats larger than
32-bits in these functions they were prevented from wrapping around to their
signed 32-bit value that we want them to return in python 2.x.