Use OS independent API for task creation/deletion

Calls to task_delete and task_spawn_cmd are now
px4_task_delete and px4_task_spawn_cmd respectively.

The px4_tasks.h header was added to the affected files
and incusions of nuttx/config.h were removed.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/modules/fixedwing_backside/fixedwing_backside_main.cpp

@@ -39,7 +39,7 @@
  * Fixedwing backside controller using control library
  */
 
-#include <nuttx/config.h>
+#include <px4_tasks.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -111,7 +111,7 @@ int fixedwing_backside_main(int argc, char *argv[])
 
 		thread_should_exit = false;
 
-		deamon_task = task_spawn_cmd("fixedwing_backside",
+		deamon_task = px4_task_spawn_cmd("fixedwing_backside",
 					 SCHED_DEFAULT,
 					 SCHED_PRIORITY_MAX - 10,
 					 5120,