A lot of GLib APIs provide a string length and explicitly say that the strings
are not NUL terminated. For instance, parsing XML using GMarkupParser or
reading packed binary strings from mmapped data files.
The global hash table we use for interned strings should not own a
reference on the strings themselves, as otherwise we'd leak them all
over the place.
Instead, it should keep a "weak" reference to them; once the last
strong reference goes away, we drop remove the weak reference from the
hash table.
The last part of the reference counting saga.
Now that we have:
- reference counter types
- reference counted allocations
we can finally add reference counted strings using reference counted
allocations to avoid creating a new String type, and reimplementing
every single string-based API.
