* lisp/erc/erc-compat.el: Do what was supposed to be done by
75f26646d4 "; Be nicer when updating
browse-url var in erc-compat". This is the less harmful version of
that patch (from bug#59976#8) but without the cl-lib requirement since
users may not want to load the main ERC library right away.
* lisp/erc/erc.el: Clarify some comments regarding the core API.