example files)

The system variable 'thread_concurrency' has been
(re-)enabled on all platforms, to prevent startup
errors.

'thread_concurrency' is unused and has no effect,
on any platform, in MySQL 5.1 and later versions.  It 
will be deprecated, and removed, in context of 
worklog WL#5265


mysql-test/include/have_thread_concurrency.inc:
  include/have_thread_concurrency.inc was only needed
  to support platforms that didn't have the
  thread_concurrency variable available.  Since the
  variable is now available on all platforms, the file
  is removed.