android usb serial: Prepare device / driver select

This commit contains the serial_android_usb part of the changes proposed
in issue #2657.

What's implemented:
- A data structure that contains all the data that can be used to
  describe an usb device (including user-facing string).
- A function to get a list of all attached usb devices (optionally with
  selectable driver class).
- Changes in the serial_android_usb_open-function and in the Java part
  to use the information about the usb device and optionally selected
  driver when connecting.

This commit keeps compatibility with the current UI-Code in the case
that only one USB-Device is connected. If two devices are connected,
only the first one is tried.

There are still some small things to do:
- Change the user-facing string to something more descriptive.
- Parts which aren't uesd anymore when the UI-Part is implemented are
  simply marked as obsolete (to keep compatibility for now).

But generally it seems to work.

[Dirk Hohndel: some white space / coding style adjustments]

Signed-off-by: Christof Arnosti <charno@charno.ch>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

core/serial_usb_android.h

@@ -0,0 +1,16 @@
+#ifndef SERIAL_USB_ANDROID_H
+#define SERIAL_USB_ANDROID_H
+
+#include <string>
+#include <vector>
+
+/* USB Device Information */
+struct android_usb_serial_device_descriptor {
+	QAndroidJniObject usbDevice; /* the UsbDevice */
+	std::string className; /* the driver class name. If empty, then "autodetect" */
+	std::string uiRepresentation; /* The string that can be used for the user interface. */
+};
+
+std::vector<android_usb_serial_device_descriptor> serial_usb_android_get_devices(bool driverSelection);
+
+#endif