[phobos] [D-Programming-Language/phobos] c91cbe: replace mutex with spinlock to reduce overhead

[GitHub via phobos]

  Branch: refs/heads/master
  Home:   https://github.com/D-Programming-Language/phobos
  Commit: c91cbef509623d115fbc49bea42b737054aac53d
      https://github.com/D-Programming-Language/phobos/commit/c91cbef509623d115fbc49bea42b737054aac53d
  Author: Martin Nowak <code at dawg.eu>
  Date:   2015-01-16 (Fri, 16 Jan 2015)

  Changed paths:
    M std/concurrency.d

  Log Message:
  -----------
  replace mutex with spinlock to reduce overhead

- spinlock yields on contention


  Commit: 92f14d8dd55987c59cedf3f68b2ef28930cc810f
      https://github.com/D-Programming-Language/phobos/commit/92f14d8dd55987c59cedf3f68b2ef28930cc810f
  Author: Martin Nowak <code at dawg.eu>
  Date:   2015-01-16 (Fri, 16 Jan 2015)

  Changed paths:
    M std/concurrency.d

  Log Message:
  -----------
  destroy node value before putting it on the freelist

- to free any owned GC memory


  Commit: 224ab42e0cd8919fdbf2ecd50249bebbd1164889
      https://github.com/D-Programming-Language/phobos/commit/224ab42e0cd8919fdbf2ecd50249bebbd1164889
  Author: Andrei Alexandrescu <andrei at erdani.com>
  Date:   2015-01-24 (Sat, 24 Jan 2015)

  Changed paths:
    M std/concurrency.d

  Log Message:
  -----------
  Merge pull request #2874 from MartinNowak/addMessageFreeList

use lock-free freelist


Compare: https://github.com/D-Programming-Language/phobos/compare/a5b1f5bcaa15...224ab42e0cd8