This is a monster patch that turns all EventTargets into GC-allocated
PlatformObjects. Their C++ wrapper classes are removed, and the LibJS
garbage collector is now responsible for their lifetimes.
There's a fair amount of hacks and band-aids in this patch, and we'll
have a lot of cleanup to do after this.
'static' for a function means that the symbol shall not be made public
for the result of the current compilation unit. This does not make sense
in a header, especially not if it's a large function that is used in
more than one place and not that performance-sensitive.