Note that constraint setting for Perms will disappear. It is no longer needed.

added alloca node

small emitter interface changes

added comments

started finish irg implementation (stack stuff)

changed spill/reload lowering (uses entities now)
changed DBG usage

moved call lowering before scheduling

fixed call requirements

removed some unused variables
added optimization to move Const's from start block into the block where they are used

changed interface names for getting codegen interface
added callbacks to codegen interface for spill/reload lowering

added callbacks for spill- and reload-lowering