src/platforms: move all headers to platforms/common/include/px4_platform_common

and remove the px4_ prefix, except for px4_config.h.

command to update includes:
for k in app.h atomic.h cli.h console_buffer.h defines.h getopt.h i2c.h init.h log.h micro_hal.h module.h module_params.h param.h param_macros.h posix.h sem.h sem.hpp shmem.h shutdown.h tasks.h time.h workqueue.h; do for i in $(grep -rl 'include <px4_'$k src platforms boards); do sed -i 's/#include <px4_'$k'/#include <px4_platform_common\/'$k/ $i; done; done
for in $(grep -rl 'include <px4_config.h' src platforms boards); do sed -i 's/#include <px4_config.h/#include <px4_platform_common\/px4_config.h'/ $i; done

Transitional headers for submodules are added (px4_{defines,log,time}.h)

platforms/common/include/px4_platform_common/shutdown.h

@@ -0,0 +1,99 @@
+/****************************************************************************
+ *
+ *   Copyright (C) 2017 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 shutdown.h
+ * Power-related API
+ */
+
+#pragma once
+
+#include <stdbool.h>
+
+__BEGIN_DECLS
+
+/**
+ * Shutdown hook callback method (@see px4_register_shutdown_hook()).
+ * @return true if it's ok to shutdown, false if more time needed for cleanup
+ */
+typedef bool (*shutdown_hook_t)(void);
+
+
+/**
+ * Register a method that should be called when powering off (and also on reboot).
+ * @param hook callback method. It must not block, but return immediately.
+ *        When the system is requested to shutdown, the registered hooks will be
+ *        called regularily until either all of them return true, or a timeout
+ *        is reached.
+ * @return 0 on success, <0 on error
+ */
+__EXPORT int px4_register_shutdown_hook(shutdown_hook_t hook);
+
+
+/**
+ * Unregister a shutdown hook
+ * @param hook callback method to be removed
+ * @return 0 on success, <0 on error
+ */
+__EXPORT int px4_unregister_shutdown_hook(shutdown_hook_t hook);
+
+
+/**
+ * Request the system to shut down or reboot.
+ * Note the following:
+ * - The system might not support to shutdown (or reboot). In that case -EINVAL will
+ *   be returned.
+ * - The system might not shutdown immediately, so expect this method to return even
+ *   on success.
+ * @param reboot perform a reboot instead of a shutdown
+ * @param to_bootloader reboot into bootloader mode (only used if reboot is true)
+ * @return 0 on success, <0 on error
+ */
+__EXPORT int px4_shutdown_request(bool reboot, bool to_bootloader);
+
+
+/**
+ * Grab the shutdown lock. It will prevent the system from shutting down until the lock is released.
+ * It is safe to call this recursively.
+ * @return 0 on success, <0 on error
+ */
+__EXPORT int px4_shutdown_lock(void);
+
+/**
+ * Release the shutdown lock.
+ * @return 0 on success, <0 on error
+ */
+__EXPORT int px4_shutdown_unlock(void);
+
+__END_DECLS
+