several bug fixes to reenable usb stick functionality

Several bugfixes made to reestablish raven usb stick functionality:
1) Due to default UIP_CONF of 128 bytes, the raven was unable to initialize. Fixed by adding UIP_CONF definition in contiki conf
2) Due to lack of default make, there was no easy command to upload the raven usb stick.
Now you can do 'make ravenusbstick.eu; make ravenusbstick.u' to write respectively eeprom and flash
3) Default programmer set to strange USB port, set to default usb port.
4) For some reason, the MAC_OS driver flag enabled caused the usb stick to not initialise properly under linux. By removing these flags, which as far as i can find are unnecessary, the usb stick initialised as usual.