ATRONIX: Support async read from clipboard

In case that read doesn't returns the data immediately, it needs to move
the data from port/state/data to port/data for later reading.

Currently the implementation assumes that the clipboard can be read in
one read when it's ready, which means a partial clipboard read is not
allowed.

(cherry picked from commit 2d7dc6e)

src/core/p-clipboard.c

@@ -50,6 +50,24 @@
 	req = Use_Port_State(port, RDI_CLIPBOARD, sizeof(REBREQ));
 
 	switch (action) {
+	case A_UPDATE:
+		// Update the port object after a READ or WRITE operation.
+		// This is normally called by the WAKE-UP function.
+		arg = OFV(port, STD_PORT_DATA);
+		if (req->command == RDC_READ) {
+			len = req->actual;
+			if (GET_FLAG(req->flags, RRF_WIDE)) {
+				len /= sizeof(REBUNI); //correct length
+				// Copy the string (convert to latin-8 if it fits):
+				Set_Binary(arg, Copy_Wide_Str(req->data, len));
+			} else {
+				Set_Binary(arg, Copy_OS_Str(req->data, len));
+			}
+		}
+		else if (req->command == RDC_WRITE) {
+			SET_NONE(arg);  // Write is done.
+		}
+		return R_NONE;
 
 	case A_READ:
 		// This device is opened on the READ: