Changes:
- Added support for Tiva C Series Launchpad. Old Stellaris Launchpads should continue to work as before.
- Switched to TivaWare from StellarisWare.
- Added support for development on Linux and Mac using GCC for ARM.
- Fixed critical UART receive buffering bug (thanks to astro75).
- Added new pwmWrite function for arbitrary PWM output.
- Added experimental support for using stdio.h functions such as printf and and sscanf. Tested only with GCC. Some functions are presently broken, such as scanf.
