This commit adds a section to the reference to document how the expander
tracks information about local bindings, and it extends some
syntax-local functions to allow them to accept multiple definition
contexts instead of just one. In addition, it improves the documentation
on how first-class definition contexts interact with local-expand,
syntax-local-value, and syntax-local-bind-syntaxes, and it also
clarifies what it means to create a child definition context.
Now with-disappeared-uses surrounds its body with let, so it can contain
multiple body expressions. The record-disappeared-use function is like
record-disappeared-uses but for a single identifier.
Port `examples`, `interactions`, etc., to use the new `examples`
form of `scribble/examples`. The main intended effect is to ensure
that errors are produced by examples only as specifically
indicated.
