ETIME was returned by cond_timedwait (sic, the pre-POSIX1001b function) on
Solaris 2.6 and 2.7. pthread_cond_timedwait on Solaris returns ETIMEDOUT.
The standard requirement is that the only additional return value
of pthred_cond_timedwait compared to pthread_cond_wait is ETIMEDOUT.
Let us not bloat the application code with redundant checks,
and if we're ever to work on a platform that returns a non-standard
value, we should write a wrapper for that platform (like we do, e.g., for
Windows).
Call pthread_mutex_destroy() on not used mutex.
Changed comments in .h and .c files from // -> /* */
Added detection of mutex on which one didn't call pthread_mutex_destroy()
Fixed bug in create_tmp_field() which causes a memory overrun in queries that uses "ORDER BY constant_expression"
Added optimisation for ORDER BY NULL