Modify the orte configure options to specify --enable-multicast such that it directs components to build or not instead of littering the code base with #if's. Remove those #if's where they used to occur.
Add a new grpcomm "mcast" module to support multicast operations. Still some work required to properly perform daemon collectives for comm_spawn operations. New module only builds when --enable-multicast is provided, and when specifically selected.
This commit was SVN r22709.
