sl/fixed_point: provide the exportControlFlow() fnc
sl/fixed_point_proxy: split plotFncCore() into two functions
sl/fixed_point_proxy: plot an extra CFG-only subgraph
sl/fixed_point: introduce the StateRewriter class
sl/fixed_point: implement StateRewriter::replaceInsn()
sl/fixed_point: implement StateRewriter::dropInsn()
sl/fixed_point: implement StateRewriter::insertInsn()