Add Rambo support/env to platformio.ini; properly maps extended pins

Marlin/platformio.ini

@@ -42,3 +42,10 @@ platform = teensy
 framework = arduino
 board = teensy20pp
 build_flags = -I $BUILDSRC_DIR -D MOTHERBOARD=BOARD_BRAINWAVE_PRO -D AT90USBxx_TEENSYPP_ASSIGNMENTS
+
+[env:rambo]
+platform = atmelavr
+framework = arduino
+board = reprap_rambo
+build_flags = -I $BUILDSRC_DIR
+board_f_cpu = 16000000L