Use @Intrinsic annotation to drive matching of magic method to magic code generators

Implement the @Intrinsic annotation as discussed in the upcoming VEE'09 paper (http://domino.research.ibm.com/comm/research_people.nsf/pages/dgrove.vee09.html). For the IA32 baseline compiler, this is plumbing + some small changes in how we map from callee method to magic generator object. For the ppc baseline compiler and the opt compiler it first requires completing the change over to MagicGenerator objects.

Once this is complete, eliminate the MagicNames class and associated Atoms, MemberRefs, etc. used for the old mapping.