Merge with armelf980813:

Merge with armelf980813:

        * rdi-share/unixcomm.c: If using cygwin32, also use the SERPORT and
        PARPORT defines for win32.
        (Unix_MatchValidSerialDevice): For cygwin32, valid serial port names
        start with "com", not "/dev/tty".
        (Unix_OpenSerial): Do not use O_NONBLOCK on cygwin32.

        * rdi-share/devsw.c (DevSW_Close): Free the device's state (SwitcherState)
        so that the device may be reopened.

        * remote-rdi.c (mywritec): Send all output through gdb's *_unfiltered
        functions, ignoring non-ASCII chars, so that non-tty UI's can snarf
        the output from fputs_hook.
        (mywrite): Ditto.
        (arm_rdi_open): Set inferior_pid.
        (arm_rdi_detach): Pop the target off the target stack so that
        users can attach and detach multiple times.
        (arm_rdi_close): Close the opened device and reset inferior_pid, too.