Since we store pointers and have an interface for iterators
set up, the count is just the distance from the beginning
to the end of the list.
Nice thing is that because of this, basic blocks also get
the ability to have a size count without needing to do anything
directly.
Small helpers for inserting nodes before and after an existing one.
insert() is the same as insert_before(), so insert() is just made
to be an alias of this.
Makes the name match the standard library equivalents.
C++17 introduces non-member empty() which allows for nicer handling
in generic contexts. May as well make the data structure compatible with
it.
The only valid objects to add to the list are those that inherit from
IntrusiveListNode. Therefore anything being added to the list that isn't
inheriting from it will cause compilation to fail.
This generalizes the regular iterator to be compatible with both use
cases. Passing in the list instance directly isn't needed, because the
only way you'd ever get a valid instantiation of an iterator is from a
list instance itself.
