Sets the FairCom DB SQL client thread priority.
Note: This feature is supported only on the Windows operating system.
priority = -3 to +3.
call fc_set_priority( 0 );
WARNING: Use extreme caution when changing this value. If the priority is set too high relative to other tasks, FairCom DB SQL may exhibit unpredictable behavior as other threads may not get enough CPU time by the process scheduler.