[3643] Fix problem on Ubuntu and NetBSD Builds

[3643] Fix problem on Ubuntu and NetBSD Builds

Both Ubuntu and NetBSD builds fail because of what appears to be an error
trying to the use "equal_range" method of one of the classes associated with
the Boost multi-index container. The cause is uncertain - other systems
build successfully, so the problem might no lie here, e.g. it could be in
the compiler.  This fix attempts to side-step the problem by modifying the
affected files so as not to use this method.