gps: major restructuring & extension of ubx driver: use a submodule for gps drivers

The gps drivers are now in a platform-independent submodule because they
are used in QGroundControl as well

.gitmodules

@@ -35,3 +35,6 @@
 [submodule "cmake/cmake_hexagon"]
 	path = cmake/cmake_hexagon
 	url = https://github.com/ATLFlight/cmake_hexagon
+[submodule "src/drivers/gps/devices"]
+	path = src/drivers/gps/devices
+	url = https://github.com/PX4/GpsDrivers.git

src/drivers/gps/CMakeLists.txt

@@ -38,10 +38,10 @@ px4_add_module(
 		-Os
 	SRCS
 		gps.cpp
-		gps_helper.cpp
-		mtk.cpp
-		ashtech.cpp
-		ubx.cpp
+		devices/src/gps_helper.cpp
+		devices/src/mtk.cpp
+		devices/src/ashtech.cpp
+		devices/src/ubx.cpp
 	DEPENDS
 		platforms__common
 	)

src/drivers/gps/definitions.h

@@ -0,0 +1,66 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2016 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file definitions.h
+ * common platform-specific definitions & abstractions for gps
+ * @author Beat Küng <beat-kueng@gmx.net>
+ */
+
+#pragma once
+
+#include <px4_defines.h>
+
+#define GPS_INFO(...) PX4_INFO(__VA_ARGS__)
+#define GPS_WARN(...) PX4_WARN(__VA_ARGS__)
+#define GPS_ERR(...) PX4_ERR(__VA_ARGS__)
+
+#include <uORB/topics/vehicle_gps_position.h>
+#include <uORB/topics/satellite_info.h>
+
+#include <unistd.h> //this is POSIX, used for usleep
+
+#include <drivers/drv_hrt.h>
+
+/**
+ * Get the current time in us. Function signature:
+ * uint64_t hrt_absolute_time()
+ */
+#define gps_absolute_time hrt_absolute_time
+typedef hrt_abstime gps_abstime;
+
+
+// TODO: this functionality is not available on the Snapdragon yet
+#ifdef __PX4_QURT
+#define NO_MKTIME
+#endif