Also updated readme to reflect change

Many of the README details and build scripts assumed environment
variables that may not exist in the open source release.
This commit cleans up much of it, and reduces the README to
what's needed.

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

moved zafl integration stage outside of for-each-function loop so integration is only inserted once, as desired

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

reworked the red-zone detector to do better than just using leaf functions, as we found the red zone used in a non-leaf function

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

When name of function is specified as entry point for fork server,
pre-insert the fork server init code at the last instruction of the
first basic block in the function.

One version returns a value. STARS is able to find a dead reg.
2nd func if void. STARS finds no dead regs.