Flush the debug stream

Testing under JTSDK MSYS environment debug info was not being seen while
running rigctl -vvvv

Adding a flush to the debug stream fixes it.

Mike W9MDB

src/debug.c

@@ -143,6 +143,7 @@ void HAMLIB_API rig_debug(enum rig_debug_level_e debug_level, const char *fmt, .
 			rig_debug_stream = stderr;
 
 		vfprintf (rig_debug_stream, fmt, ap);
+		fflush(rig_debug_stream);
 	}
 
 	va_end(ap);