wkb.c: cb_cmd_fifo_in(): Handle G_IO_STATUS_EOF correctly.
wkb.c: cb_cmd_fifo_in(): Handle G_IO_STATUS_EOF correctly.

Under OpenBSD, the old code caused an infinite loop if the pipe was
closed (this behavior was not present under Linux).

bmc0/wkb,bmc0/wkb,bmc0/wkb,bmc0/wkb