sl/adt_op_meta: do not emit MO_UNSET due to abstraction
sl/adt_op_replace: fix true/false order in crHandleLoc()

... swapped by mistake
sl/adt_op_replace: do not stop on failed independency check
sl/adt_op_replace: support dst accessors in replaceBound()

This is not the best possible solution but we stay on the safe side.
sl/fixed_point_rewrite: drop orphan backward edges in mergeInsns()
sl/fixed_point: hook the tryRemoveDeadBranches() pass
sl/fixed_point: actually implement removeDeadBranch()
sl/fixed_point: let removeDeadBranch() remove the branch insn