Monotone chain algorithm for finding a convex hull in 2D
Description
This is somewhat experimental still.
This (XS) module optionally exports a single function C<convex_hull>
which calculates the convex hull of the input points and returns it.
The algorithm is C<O(n log n)> due to having to sort the input list,
but should be somewhat faster than a plain Graham's scan (also C<O(n log n)>)
in practice since it avoids polar coordinates.