Fix the empty MCU Type combo list

In recent version of GCC, the default output of --target-help doesn't include the list of supported devices by default,
unless the -Wa,-mlist-devices option is set.
Merge remote-tracking branch 'github-jawher/known-mcu-list' into R2.4_Maintenance
Solved bug #60 AVRDude verbose option breaks programming

The verbose option of avrdude was outputting a line like this
  avrdude: usbdev_open(): Found AVRISP mkII, serno: 000200129194
and that was seen as a fatal error because the word usbdev_open
was found.
The change has also been made in AvariceOutputListener.java but it
has neither been tested nor do I know if the bug exists for avarice.