ACPI entity definitions form a tree whose roots are a sequence of
pre-defined namespace objects. The parser stores all AML entities using
a space-optimized structure (Object). These objects are organized into a
tree via the ObjectTree structure.
Instead of storing pointers to other objects (i.e. siblings, children or
parent), objects use uint32 indices to objects managed by the
ObjectTree. This has the nice advantage of reducing the memory
requirements for our tree in half when running on 64-bits (4-bytes per
index vs 8-bytes per pointer) while also allowing us to recycle objects
that are explicitly freed by the parser.
