crash readout: master i2c should go into known state

message_buffer_end symbol address is wrong

check output file davenant:trains-bessar/detpic/cro2
 this does correspond to current code and shows a bug in point init'n

then when point init'n ok, move panic morse_TI2 in slave.asm along
 and debug next bit


layout polarity diagram colourful segment encoding:
 make moveable feature selection in subseg2display bitwise rather than
  setwise

safety system no crashes at crossovers please