[goal] Add labels, break, and continue to loops

[Brent-Hickey]

Uses (block) and (return-from) to support (break) and (continue) with labeling

Supports (while) (until) (dotimes) (countdown) (loop) (doarray)

Test cases:

(dotimes (i 5)
    (when (= i 2)
        (break)
    )
    (format #t "i: ~D~%" i)
)
;; Output:
;; i: 0
;; i: 1

(dotimes (i 5)
    (when (= i 2)
        (continue)
    )
    (format #t "i: ~D~%" i)
)
;; Output:
;; i: 0
;; i: 1
;; i: 3
;; i: 4

(dotimes (i 3)
    (when (= i 2)
        (continue)
    )
    (format #t "outer: ~D~%" i)
    (dotimes (i 3)
        (when (= i 0)
            (continue)
        )
        (format #t "inner: ~D~%" i)
    )
)
;; Output:
;; outer: 0
;; inner: 1
;; inner: 2
;; outer: 1
;; inner: 1
;; inner: 2

(dotimes (i 5) :label outer
    (when (= i 2)
        (continue :from outer)
    )
    (format #t "outer: ~D~%" i)
    (dotimes (i 3)
        (when (= i 1)
            (continue :from outer)
        )
        (format #t "inner: ~D~%" i)
    )
)
;; Output:
;; outer: 0
;; inner: 0
;; outer: 1
;; inner: 0
;; outer: 3
;; inner: 0
;; outer: 4
;; inner: 0

(dotimes (i 5) :label outer
    (when (= i 2)
        (continue :from outer)
    )
    (format #t "outer: ~D~%" i)
    (dotimes (i 3)
        (when (= i 0)
            (break :from outer)
        )
        (format #t "inner: ~D~%" i)
    )
)
;; Output:
;; outer: 0

(dotimes (i 5) :label outer
    (when (= i 2)
        (continue :from outer)
    )
    (format #t "outer2: ~D~%" i)
    (dotimes (i 3)
        (when (= i 1)
            (break)
        )
        (format #t "inner2: ~D~%" i)
    )
)
;; Output:
;; outer2: 0
;; inner2: 0
;; outer2: 1
;; inner2: 0
;; outer2: 3
;; inner2: 0
;; outer2: 4
;; inner2: 0

(countdown (i 5)
    (when (= i 2)
        (continue)
    )
    (format #t "i: ~D~%" i)
)
;; Output: 
;; i: 4
;; i: 3
;; i: 1
;; i: 0

(let ((i 0))
    (while (< i 5)
        (when (= i 1)
            (break)
        )
        (format #t "i: ~D~%" i)
        (1+! i)
    )
)
;; Output: 
;; i: 0

(let ((i 0))
    (until (> i 5) :label outer
        (loop
            (break :from outer)
        )
        (format #t "i: ~D~%" i)
        (1+! i)
    )
)
;; Output:
;; nothing

(define *array* (new 'global 'boxed-array uint32 3))
(doarray (i *array*)
   (break)
   (format #t "doarray")
)
;; Output:
;; nothing

(doarray (i *array*) :label arrayloop
    (dotimes (i 5)
        (when (= i 2)
            (continue :from arrayloop)
        )
        (format #t "i: ~D~%" i)
    )
    (format #t "doarray~%")
)
;; Output:
;; i: 0
;; i: 1
;; i: 0
;; i: 1
;; i: 0
;; i: 1