Log Message:
Updated devel/ck (concurrencykit) 0.4.1 to 0.5.1
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(From: https://github.com/concurrencykit/ck/releases)
0.5.1 on 31 Dec 2015
- regressions/ck_sequence: Use flag rather than counter value for first set.
- Prevents resetting exit barrier on overflow. Otherwise, hangs occur
  on higher-performing systems.

0.5.0 on 2 Nov 2015
- ck_epoch: Fix typo (affects RMO targets).

0.4.5 on 19 Dec 2014
- build: Bump version for next release.

0.4.4 on 2 Sep 2014
- whitespace: Remove extraneous lines.

0.4.3 on 31 Jul 2014
- regressions/ck_stack: Align stack for cmpxchg16b.

0.4.2 on 23 Apr 2014
- build: Bump version for release.