Did a bunch of grepping for `moz*` and searched for "moz" in rustdoc,
deleting anything that looked mozilla-specific. Now there's nothing left
with the "moz" prefix in rustdoc!
I think these might all be from before WebIDL mixins existed. Either way,
multiple inheritance of interfaces that don't have exposed interface objects is
equivalent to mixins.
* Add renaming of conflicting constructors and operations
* Rename conflicting to overloaded
* Fix newlines
* Use or_insert_with, add a comment to TypeToString
* Use more Rust-like names
* Use opt instead of nullable
* Use argument names instead of argument types if possible
* Drop new for overloaded constructots
* Remove extra newline
* Move WebIDL files from unavailable_overloaded_fn
* Move RTCDataChannel, RTCPeerConnection and Selection to unavailable_option_primitive
