Change load to take a second argument which is the environment to load into. The default is (interaction-environment).
See also #161.
On reflection, the interaction-environment is the only standard environment that is mutable, so there's no need to add this argument to the standard, simply to specify that load mutates the interaction environment. Schemes with first-class environments can add the second argument as an extension, but we need not say so.
WG1 accepted this proposal.