Add STB board support to Marlin (next step towards graphic LCD implementation)

This is the second part of modifications necessary for the graphics lcd support which is using a modified Sanguino hardware.

It adds support for the STB board V1.1 which is the reference hardware on which i test the implementation. Alle necessary defines for the GLCD are already in it.

Next step will be the pull request for the graphics library and the graphics driver.

--> see pull request #408 (already commited)
--> see pull request #399 which contains all necessary changes in one request.