Make a printable version of the MD5 sum. This converts
a non-printable 16-byte (128-bit) key to ASCII.
MD5Sum() explains how to generate the checksum.
Parameters:
key - 16-byte buffer with the key after MD5Init(), MD5Update() and MD5Final() are done. ascii - A buffer of 32 bytes and a NULL terminator,
preferably, to hold the printable key.