Log Message:
Updated afl to 2.51b.

---------------------------
Version 2.51b (2017-08-30):
---------------------------

  - Made afl-tmin call setsid to prevent glibc traceback junk from showing
    up on the terminal in some distros. Suggested by Jakub Wilk.

---------------------------
Version 2.50b (2017-08-19):
---------------------------

  - Fixed an interesting timing corner case spotted by Jakub Wilk.

  - Addressed a libtokencap / pthreads incompatibility issue. Likewise, spotted
    by Jakub Wilk.

  - Added a mention of afl-kit and Pythia.

  - Added AFL_FAST_CAL.

  - In-place resume now preserves .synced. Suggested by Jakub Wilk.