Changed IGNORE_RESULT() to avoid warnings when compiling with clang.
ut_frag_pmsg_free(): rescheduling of expire event was in wrong block.

If the message is unreliable and there is only one fragment, sending the
fragment means the whole message is immediately freed, since there is nothing
to acknowledge, hence we cannot access the message after ut_frag_free() has
been called.
base16_encode(): fixed grave bug: buffer overflow if destination too small.
search_results_handle_trailer(): fixed improper buffer size to log wrong token.
sectoken_generate_n(): avoid magical constants.
search_oob_pending_results(): added trace of generated token, when debugging.
Rotate OOB token keys less often, to make sure no expiration occurs in transit.
Raised OOB_REPLY_ACK_TIMEOUT to 15 minutes.

Remote servents have been seen providing OOB replies (with a proper token,
hence completely valid) after 11 minutes.  Raising the bar to 15 minutes
should be safe.