`exact-integer-sqrt``K`procedureReturns two values

`s`and`r`, where`s^2 + r = K`and`K < (s+1)^2`. In other words,`s`is the closest square root we can find that's equal to or smaller than`K`, and`r`is the rest if`K`isn't a neat square of two numbers.This procedure is compatible with the definition from the R7RS

`(scheme base)`library.