Previously, if avrdude skipped the upload step the read while write memory might never be reenabled. This would prevent the bootloader from ending and the sketch from starting - the bootloader just continued to run even after a successful upload. Now enable RWW when we receive the AVR109 "Exit bootloader" 'E' command. Had to disable lock bit changing support in the bootloader to free up flash for the change - will anyone miss it?
attempt to fix bug reported by Dave Mellis:
"avrdude: ser_close(): can’t reset attributes for device: Invalid argument"
is thrown after attempting an upload in the IDE (though the upload seems to be successful)
Earlier approach had bootloader end as soon as it was told to. On Linux this caused problems with avrdude because the microcontroller never had a chance to send an acknowledgement.
