Initialized tty->refcount to 0. When (for whatever reason) malloc()

returned a buffer which was not zero-filled, the reference count
was not correct.  When the application exitted, the "lastClose"
handler was not being called to flush the output.  This problem
had manifested itself on a variety of platforms.

The function rtems_termios_dequeue_characters() incorrectly incremented
the buffer pointers when it was invoked and there were no characters
in the ring buffer.  This problem had also manifested itself on a
variety of platforms.  The symptom was a strange repeating of the
data in the transmitter buffer when the transmitter serial device
was supposed to go idle.

c/src/lib/libc/termios.c

@@ -219,6 +219,7 @@ rtems_termios_open (
 
 		tty->minor = minor;
 		tty->major = major;
+		tty->refcount = 0;
 
 		/*
 		 * Set up mutex semaphores
@@ -922,6 +923,8 @@ rtems_termios_dequeue_characters (void *ttyp, int len)
 
 	if (tty->rawOutBufState == rob_wait)
 		rtems_semaphore_release (tty->rawOutBufSemaphore);
+	if ( tty->rawOutBufHead == tty->rawOutBufTail )
+		return;
 	newTail = (tty->rawOutBufTail + len) % RAW_OUTPUT_BUFFER_SIZE;
 	if (newTail == tty->rawOutBufHead) {
 		/*