RIB Modifications and Optimizations + some BUG fixes

Hi Ben,

I had some other obligations on my work, so I've put XORP development a little on the side for a last few months.

Any how, I had some RIB modification and optimization patches and some BUG fixes that were sitting on my tree. 
I've rebased them on the top of the XORP master branch, and this is the pull request for them.

They've passed all XORP tests.

BR
Igor

PS. Please post this to the xorp-hackers group. I can't do it from GitHub.