Wakaama logs arbitrary bytes to stdout

[mlasch]

When logging is enabled, Wakaama sends arbitrary bytes to stdout.

Examples:

wakaama/core/packet.c

Line 494 in 22bf6e1

LOG_ARG("Payload: %.*s", (int)message->payload_len, STR_NULL2EMPTY(message->payload));

wakaama/core/uri.c

Line 227 in 22bf6e1

LOG_ARG("buffer_len: %zu, buffer: \"%.*s\"", buffer_len, (int)buffer_len, STR_NULL2EMPTY(buffer));

wakaama/data/json.c

Line 496 in 22bf6e1

LOG_ARG("bufferLen: %zd, buffer: \"%.*s\"", bufferLen, (int)bufferLen, STR_NULL2EMPTY((char *)buffer));

wakaama/data/senml_json.c

Line 612 in 22bf6e1

LOG_ARG("bufferLen: %zd, buffer: \"%.*s\"", bufferLen, (int)bufferLen, STR_NULL2EMPTY((char *)buffer));

We should implement a hexdump functionality for logging.