exchanged BOARD_BLACKLIST with FEATURES_REQUIRED in the example Makefile
added cpp as feature for board native
Merge pull request #1988 from BytesGalore/riot_and_cpp_blacklist_to_required_feature

examples/riot_and_cpp: exchanged BOARD_BLACKLIST with FEATURES_REQUIRED
removed `_kill_r` already provided by newlib
added `_kill` stub
added missing `CXX` flags
[SQUASH ME] added cpp feature to arduino-due board