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/drivers/device/device_posix.cpp

@@ -83,7 +83,7 @@ Device::log(const char *fmt, ...)
 {
 	va_list	ap;
 
-	printf("[%s] ", _name);
+	PX4_INFO("[%s] ", _name);
 	va_start(ap, fmt);
 	vprintf(fmt, ap);
 	va_end(ap);