[plt-scheme] slightly misleading error message

Danny Yoo wrote:

>> set!: expected a defined name after `set!', but found a function 
>> argument name
> 
> That sounds like a correct error message to me.  What part do you feel 
> is misleading about it?

Hmmm. I could have sworn it said "function name", not "function argument 
name". I guess I misread it. It's a perfectly correct error message. My 
apologies for the noise. --PR