======Synopsis:======
$[[b64decode]](//<stuff>//)

======Returns:======
Returns the inverse RFC1421 transformation of //<stuff>//, commonly known 
as Base64.  The inverse transformation converts four Base64 digits into 
three bytes.

Alas, because ircII only supports C strings, if //<stuff>// decodes to 
binary data (with nuls) it will probably not do what you hope.

The reverse transformation is [[b64encode]].

Don't confuse this encoding with the one used by FiSH (popularized by eggdrop 
and other irc clients for encrypted messages).  FiSH uses l64a encoding, and 
can be decoded using the [[xform]] FISH64 transform.

======Returns:======
The rfc1421 string //<stuff>// converted into a C string.