Add CC2420 support to TOSSIM.

Code that uses CC2420's features like Snoop, getRSSI, setChannel etc can now be simulated under TOSSIM.

Changes are adapted from http://hinrg.cs.jhu.edu/git/?p=mike/tinyos-2.x.git
Added RadioPacketMetadataC to match new BLIP architecture
Merge pull request #167 from srikanthnv/cc2420_tossim

Adding CC2420 support to TOSSIM.