Revision 2506

Update of the src/include/spd.h file with the following improvements:

 * Added information on the relevant datasheet(s) and where to get them.
 * Added missing #defines for some other config bytes.
 * Documented all config bytes a bit better.
 * Renamed some #defines to hopefully make their names clearer. 

(closes #38)

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Stefan Reinauer <stepan@coresystems.de>