cmp-length - compare the length of two series and return -1, 0, or 1, to support stable sorts by length
; Support func for stable sort comparator
cmp-length: func [a [series!] b [series!] /local len-a len-b] [
len-a: length? a
len-b: length? b
case [
len-a < len-b [-1]
len-a > len-b [1]
len-a = len-b [0]
]
]