tinydtls.h: include dtls_config.h in tinydtls.h Fixes dtls_config.h not visible in headers Include dtls_config.h in tinydtls.h and include tinydtls.h in all necessary headers. Remaining headers do not use 'ifdef', but they may require it too. Change-Id: I39c86dffc8bbc8bd7551e74386994f92f49d00ec Signed-off-by: Gaëtan Harter <gaetan.harter@inria.fr>