[R6RS] a typo and some lexical issues

[Anton van Straaten]

Michael Sperber wrote:
> #VU8(...)
> #Vu8(...)
> #vU8(...)
> 
> ?
> 
> My gut feeling is no, but I'm unsure what the rationale for that would
> be.

Since Scheme is now case-sensitive, supporting alternate cases on some 
things doesn't make much sense.