mavlink: cmake generate mavlink headers at build time

- mavlink/mavlink is now directly included as a submodule instead of the generated mavlink/c_library_v2
 - this also switches to mavlink development.xml by default

src/modules/mavlink/mavlink_bridge_header.h

@@ -61,7 +61,7 @@
 # define MAVLINK_COMM_5 static_cast<mavlink_channel_t>(5)
 #endif
 
-#include <v2.0/mavlink_types.h>
+#include <mavlink_types.h>
 #include <unistd.h>
 
 __BEGIN_DECLS
@@ -92,7 +92,7 @@ void mavlink_end_uart_send(mavlink_channel_t chan, int length);
 extern mavlink_status_t *mavlink_get_channel_status(uint8_t chan);
 extern mavlink_message_t *mavlink_get_channel_buffer(uint8_t chan);
 
-#include <v2.0/standard/mavlink.h>
+#include <mavlink.h>
 
 __END_DECLS