add rlibmap a utility used to build a map between classes and libraries.

The rlibmap utility will create a system.rootlibmap file used to load the
library for an unknown class. To be enabled in the very near future.


git-svn-id: http://root.cern.ch/svn/root/trunk@7733 27541ba8-7e3a-0410-8455-c3a389f83636