v6502: Add RTS BIT
v6502: Add RTS BIT

- Have to split v6502_Q (combined Z and N) into v6502_Qz and v6502_Qn,
  because BIT can yield Z=1 and N=1 (which is also the case for for PLP
  and RTI later, so the idea of a single v6502_Q was too good to be
  true anyhow). All instructions updated accordingly. PCL pegging
  to to keep v6502_ADC within 38 cycles.

Not tested. 6 to go.

kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom