Make 'ok' always do a single I/O operation.
Make 'ok' always do a single I/O operation.

Means t/concurrency/01-thread.t output will not be garbled.

cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp