Update libevent from 2.1.5-beta to 2.1.7-rc.

  - Fixes bug in signal handler cleanup in 2.1.5-beta
  - Make sure /usr/include/event.h and friends are deprecated like
    in staging to avoid accidental includes.

Change-Id: Id5fd60d2b8aaa10b7a3a5e60b397289982154c8c
1 file changed