sched/task_terminate always return an error because return value was not being set correctory.  From Gosha

Back out part of write buffering change.  David G reports that this causes problems connecting to a server

Minimal changes to get a clean compilation of the SAMD20 Xplained configuration. Still a lot of missing logic

Add configuration for the SAMD20 Xplained Pro board.  Initial check a low-effor, unverified clone of thoe SAM4L Xplained Pro board configuration