POSIX: Improved logging

The warnx and warn calls map to PX4_WARN.
Calls to errx or err genrtate a compile error.

The px4_log.h file implements a new log format:

For DEBUG and INFO:
<level> <msg>

For ERROR and WARN:
<level> <msg> (file filepath line linenum)

The verbosity can be changed by setting the macro to use
either linux_log or linux_log_verbose in px4_log.h

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

src/platforms/qurt/px4_layer/px4_qurt_tasks.cpp

@@ -264,7 +264,7 @@ void px4_show_tasks()
 	for (idx=0; idx < PX4_MAX_TASKS; idx++)
 	{
 		if (taskmap[idx].isused) {
-			PX4_INFO("   %-10s %u", taskmap[idx].name.c_str(), taskmap[idx].pid);
+			PX4_INFO("   %-10s %lu", taskmap[idx].name.c_str(), taskmap[idx].pid);
 			count++;
 		}
 	}