Add missing documentation to custom BuiltTest hardware mapping files. Fix up old copyright years on some makefiles.

Fixed compile error with the unreleased ATMEGA32U6 device.

Add branch for the conversion of demos to use standard C header files for configuration, rather than makefile defined macros.

Speed up build tests by only building each test to the ELF output stage (when all files are compiled and linked), rather than to the full HEX output stage as the resulting binary is not actually required.