Porting Stellaris Launchpad board (LM4F120)

Hello,

I have ported RIOT-OS to Stellaris Launchpad LM4F120 board. This is just a basic port with currently only TIMER, and UART modules supported.

I have re-structured this in accordance to the new structuring that RIOT has implemented.

These boards are very low cost and powerful boards. The LaunchPad board features an 80MHz LM4F120H5QR microcontroller, on-board emulation and BoosterPack XL format expansion pins. The LM4F120H5QR microcontroller has 256KB of flash memory, 32KB of RAM, 2KB of EEPROM,

Thanks and Regards, Rakendra