Revision 3766

Fixed deadlocks (e.g. when restarting engines).

* Individual thread implementations (e.g. disk thread, etc.):
  Disable thread cancellation on critical sections, e.g. when holding
  mutex locks, to prevent deadlocks if thread is stopped and/or
  restarted.

* Added TestCancel() calls to thread implementations if missing.

* No need to wrap Thread::TestCancel() calls into
  CONFIG_PTHREAD_TESTCANCEL macro conditions (since TestCancel() is
  already a stub on systems which don't have pthread_testcancel()
  available).

* If compiled for debugging: give each thread a human readable name
  to simplify debugging of multi-threading issues.

* DiskThreadBase: TestCancel() and pthread_testcancel() calls are
  per-se redundant, so only call TestCancel().

* Added missing override keywords to silent compiler warnings.

* Bumped version (2.1.1.svn54).