Add initial RT-3 AVR port

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@6998 35acf78f-673a-0410-8e92-d51de3d6d3f4
AVR HAL ported from RT-2 (serial/pal/hal tested)

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@6999 35acf78f-673a-0410-8e92-d51de3d6d3f4
Updated to RT-3 (might temporarily break NIL port)

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@7000 35acf78f-673a-0410-8e92-d51de3d6d3f4
Initial RT-3.0 Arduino Mega port

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@7001 35acf78f-673a-0410-8e92-d51de3d6d3f4