Copy some files from cpu/sam3x8e to cpu/cc2538.
Add the latest cc2538-bsl script from https://github.com/JelmerT/cc2538-bsl/commit/f3701a0
Add support for the Texas Instruments CC2538 ARM Cortex-M3 MCU and developer kit.
Merge pull request #1697 from locicontrols/cc2538

Add support for the Texas Instruments CC2538 ARM Cortex-M3 MCU and developer kit.