[plt-scheme] MD5 in v299.400

I don't understand the discrepancy between the definition of md5 in  
md5.ss, and the one which is provided by (require (lib "md5.ss")).

I don't understand why md5 requires a byte-string argument, instead  
of a string.

The test code in "md5.ss" does not evaluate, because arguments are  
the wrong type.

If the definition of md5 in md5.ss is not the one which is actually  
provided by (require (lib "md5.ss")), then where or how is md5 being  
defined?

Apparently I am missing something very basic about either scheme  
itself, or PLT scheme specifically.

- dr