initialize serial console on arduino

This hardcodes to DEFAULT_BAUD_RATE in jshInit directly, bypassing the
console setup architecture that seems to be present. However, I wasn't
quite certain how to properly call those functions and adding this at
least makes things work on Arduino.
Don't litter the arduino serial console with colons

For some reason there was a colon printed after every character, that
messes up the layout. This removes the extra print.
support Arduino 1.5.x as well

This added some extra source files, which are now (conditionally) listed
in the Makefile as well.
when compiling for arduino, generate a .hex file

This is the default format used for uploading using avrdude.
replace --relax with -mrelax

--relax is a linker option that should be passed to ld directly. Since
gcc is called to do the linking, -mrelax must be used (which tells gcc
to pass --relax to the actual linker)
Merge pull request #418 from matthijskooijman/arduino

Some additional improvements for Arduino