This commit adds a new class to opal: opal_interval_tree_t. This is a
thread-safe impelementation of a 1-dimensional interval tree. The data
structure is intended to provide a faster implementation of the
registration cache VMA tree.
The thread safety is provided by a relativistic red-black tree
implementation. This structure provides support for multiple-reader,
and single writer. There is one caveat, an item may appear in the tree
twice while the tree is being updated. Care needs to be taken to avoid
issues associated with this "feature". I don't anticipate a problem
with the current VMA tree usage.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
