Bug#55001 Change in behavior: thread_concurrency (docs,

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/suite/sys_vars/t/thread_concurrency_basic.test

@@ -1,4 +1,3 @@
---source include/have_thread_concurrency.inc
 #
 # only global
 #