zafl updates to instrument only loop headers.  refactored slightly to deal with critical edge breaker and loop header cfg changes outside of zax_base class because zax_base constructor was creating a cfg for use later, and these xforms where modifying the cfg.  consider: move CEB and Zedge to their own xform

setup critical edge breaking to 1) emit a map of critical edges, and 2) parameterize which edge types get broken

updating zafl.sh and zax to using command line args instead of env for communicating fixed-map addressing