[ros-svn] [hpoussin] 14490: Correct IOCTL_SERIAL_CLEAR_STATS and IOCTL_SERIAL_PURGE

[hpoussin at svn.reactos.com]

Correct IOCTL_SERIAL_CLEAR_STATS and IOCTL_SERIAL_PURGE
Manage read errors (overrun, parity, ...)
Use output buffer even if Uart is ready to transmit


Updated files:
trunk/reactos/drivers/dd/serial/devctrl.c
trunk/reactos/drivers/dd/serial/misc.c
trunk/reactos/drivers/dd/serial/rw.c
trunk/reactos/drivers/dd/serial/serial.h