This is an ordered range sequence used to keep track of free address
ranges.

The sequence contains an entry for every free address range, with base
pointing to the first free address and end pointing to the next first
used address. It is initialized to [0, ~0] for convenience, so that
there's always a range before or after a view.

In the worst case scenario, where memory is entirely fragmented, there's
going to be one more range than allocated views, but in general there's
much less. In any case, because of cache locality, iterating in the
contiguous sequence is much faster than traversing the view rbtree.

In theory there can be a performance hit when allocating or deleting a
view, as we may have to move the end of the sequence when a range is
split or merged. But in practice and given the usually low number of
ranges, this is not an issue.

The default and maximum sequence size can hold up to 65536 ranges, which
is much more than enough in general, and performance is probably going
to be bad before reaching the limit anyway. The code currently asserts
when reaching the limit, although we could possibly grow the sequence.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>