libgfortran/ChangeLog:
* io/transfer.c (st_read_done_worker, st_write_done_worker):
Call unlock_unit here, add unit_lock lock around newunit_free call.
(st_read_done, st_write_done): Only call unlock_unit when not
calling the worker function.
* io/unit.c (set_internal_unit): Don't reset the unit_number
to the same number as this cause race warnings.