Merge pull request #356 from oliverschmidt/master

Allow text screen memory to be aligned to 0x2000.
Updates CC2538 GPIO

1. Fixes two of the comments to GPIO macros. They were copied but not
updated.
2. Adds SET and CLR macros for controlling GPIO pins.
Add conf checks to CC2538dk conf file

Allows for specific apps to control more settings of the platform.
Merge pull request #355 from lab11/cc2538dk-conf-defines

Add conf checks to CC2538dk conf file
Merge pull request #353 from lab11/cc2538-gpio

Updates to CC2538 GPIO
Optimized CS8900A driver for speed and size.

- Speed: The primary byte copy loops are reduzed to the bare minimum by adjusting the base pointer 'ptr' and loop register 'y' in such a way that the 'y' overflow matches the low byte of the loop size.

- Size: Factored out all repeated code into subroutines. Introduced a loop for setting the MAC address.

Additional minor changes:

- Activate frame reception as last step of initialization after CS8900A configuration.

- Properly set internal address bits used by the CS8900A.
- Optimized LAN91C96 driver for speed and size.

- Speed: The primary byte copy loops are reduzed to the bare minimum by adjusting the base pointer 'ptr' and loop register 'y' in such a way that the 'y' overflow matches the low byte of the loop size.

- Introduced a loop for setting the MAC address.

Additional minor fix:

- Properly start self modification with first location.