Address generator feedback

Address generator feedback

* doc/lispref/control.texi (Generators): Correct missing word.  Clarify which
forms are legal in which parts of `unwind-protect'.  Fix orphaned
close parenthesis.

* lisp/emacs-lisp/generator.el: Make globals conform to elisp
style throughout.  Use more efficient font-lock patterns.
(cps-inhibit-atomic-optimization): Rename from
`cps-disable-atomic-optimization'.
(cps--gensym): New macro; replaces `cl-gensym' throughout.
(cps-generate-evaluator): Move the `iter-yield' local macro
definition here
(iter-defun, iter-lambda): from here.

* test/automated/generator-tests.el (cps-test-iter-close-finalizer):
Rename `gc-precise-p' to `gc-precise'.

* test/automated/generator-tests.el (cps-testcase): Use
`cps-inhibit-atomic-optimization' instead of
`cps-disable-atomic-optimization'.