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

More changes to reduce complaints from CppCheck.  Some latent bugs fixes, but probably some new typos introduced

Many changes to reduce complaints from CppCheck.  Several latent bugs fixes, but probably some new typos introduced