This adds an O(1) check at the head of the lookup to avoid looking at
every RB_RIGHT() in the tree when address falls beyond the upper bound of
the interval tree.
This uses an augmented red-black tree to create an interval tree with
non-interval lookups. That amounts to storing address ranges within the
red-black tree, but looking up by single address.
This relies on begin/end range for the symbols to create something akin to
an interval tree, albeit with GSequence. If performance needs to be
addressed, can probably augment SysprofSymbol for an interval rbtree.
