Improved the bytecode optimizer. * Can now test for basic blocks. * Optimize inverted comparisions. * Optimize unary_not followed by a conditional jump. * Added a new opcode, NOP, to keep code size constant. * Applied NOP to previous transformations where appropriate. Note, the NOP would not be necessary if other functions were added to re-target jump addresses and update the co_lnotab mapping. That would yield slightly faster and cleaner bytecode at the expense of optimizer simplicity and of keeping it decoupled from the line-numbering structure.