These are equivalent to their racket for loop counterparts, and creates
an iterator that signals exhaustion befor or after yielding a value
where a predicate returns true. Not useful in non-nested loops, but
could be useful in inner loops where you want to exit to an outerloop
instead of :break-ing.
Also fixed some bugs in other generator clauses.
The third clause (the "check" clause) now breaks the entire
iteration for :acc clauses instead of just exiting the current subloop.
This is much saner, and was immediately usable in vectoring.
There is no need for :acc clauses to intoduce loop variables, or for :for clauses to introduce acc clauses.
They are now changed.
* goof.scm (cl-next/acc cl-next/for): removed the unused matchings for loop-vars and acc-vars respectively.
* goof/iterators.scm (all iterators): simplified it.
