Better checking of -c option in zafl.sh.  updates to ceb.map and zax.map to support Zuntracer style patching of critical edge jumps

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

Building CFGs seems to require that the assembly is correct
Force building of the assembly after making mods to the IR
and before building a new CFG