#3 (load ...) using URL

[Michael Binz]

The (load ...) function should support loading from an
URL. Important is to be able to load relative files, ie. if a
file in directory x performs a (load "puh.scm"), then
x/puh.scm is loaded.

This should also work for code loaded from a jat file, like
the runtime.

Other options like loading from the internet are cool but
less important.