tests for num-within and within
moved tests for `within` to its own suite (test-within.arr)
rename local function `within` to `localwithin` so as not to clash
with new primitve `within`
`equal3` takes fourth (optional) argument `tol`.
New function `within` takes a single tolerance argument and
uses the 4-argument equal3 to perform equality comparisons of Pyret
objects, with number equality done only up to that tolerance.
added `within`
added `within`