Added header files for Silicon Laboratories (formerly Cygnal) CPUs

Added header files for Silicon Laboratories (formerly Cygnal) CPUs
converted by Maarten Brock. The original cygnal license prohibited inclusion into SDCC.
On 2004-01-19 Maarten has received permission from <mcutools@silabs.com>: "We are currently in the process of removing the copyright notices from our header files. So, feel free to do what you like with them". We maybe will change later from LGPL to whatever license shows up on the silabs website.

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@3162 4a8a32a2-be11-0410-ad9d-d568d2c75423