[CM] Delimited strings in s7

[Elijah Stone]

On Sun, 4 Apr 2021, Elijah Stone wrote:
> Ah--it seems *#readers* can do this easily already.

I do notice it's difficult to define new token types, though, because of 
the 'read until next delimiter' behaviour.  In order to get correct 
behaviour in all cases, I need make a wrapper port and use 'read' and 
'values'.  Which is a bit inconvenient.

Proposed behaviour: if a niladic function is put in *#readers*, no 
additional characters will be read past the #.  Thoughts?

(I'll post a patch tomorrow; late today.)