Fix auto-reset on Leonardo-derived boards from Linux hosts

Also renamed the touchPort() function, as it's now unambiguously
single-purpose.

The 1200bps reset from Linux hosts wasn't working with these newer
JSSC-based versions. Adding a step which explicitly sets DTR low (via a
TIOCMSET ioctl clearing DTR) fixes this.

I'm fairly sure the reason why this worked on older Arduino with librxtx
and not with jssc is that librxtx appears to keep HUPCL in the termio
flags, but jssc appears to remove it. If HUPCL ("hangup on close") is
set, it causes DTR to be explicitly pulled low on close.

arduino-core/src/cc/arduino/packages/uploaders/SerialUploader.java

@@ -116,7 +116,7 @@ public boolean uploadUsingPreferences(File sourcePath, String buildPath, String
           if (verbose)
             System.out.println(
               I18n.format(_("Forcing reset using 1200bps open/close on port {0}"), uploadPort));
-          Serial.touchPort(uploadPort, 1200);
+          Serial.touchForCDCReset(uploadPort);
         }
         Thread.sleep(400);
         if (waitForUploadPort) {

arduino-core/src/processing/app/Serial.java

@@ -80,11 +80,12 @@ public Serial(String iname) throws SerialException {
             new Float(PreferencesData.get("serial.stopbits")).floatValue());
   }
 
-  public static boolean touchPort(String iname, int irate) throws SerialException {
+  public static boolean touchForCDCReset(String iname) throws SerialException {
     SerialPort serialPort = new SerialPort(iname);
     try {
       serialPort.openPort();
-      serialPort.setParams(irate, 8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
+      serialPort.setParams(1200, 8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
+      serialPort.setDTR(false);
       serialPort.closePort();
       return true;
     } catch (SerialPortException e) {