Create development.xml and seed with MISSION_CHECKSUM (mavlink#1611)

message_definitions/v1.0/all.xml

@@ -7,6 +7,7 @@
   -->
   <include>ASLUAV.xml</include>
   <include>common.xml</include>
+  <include>development.xml</include>
   <include>icarous.xml</include>
   <!-- matrixpilot.xml: ERROR: Duplicate message id 150 for FLEXIFUNCTION_SET (matrixpilot.xml:50) also used by SENSOR_OFFSETS (ardupilotmega.xml:1101) -->
   <!-- <include>matrixpilot.xml</include> -->

message_definitions/v1.0/development.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0"?>
+<mavlink>
+  <!-- XML file for prototyping definitions for standard.xml  -->
+  <include>standard.xml</include>
+  <version>0</version>
+  <dialect>0</dialect>
+  <enums>
+    <!-- none defined (yet) -->
+  </enums>
+  <messages>
+    <message id="53" name="MISSION_CHECKSUM">
+      <wip/>
+      <!-- This message is work-in-progress and it can therefore change. It should NOT be used in stable production environments. -->
+      <description>Checksum for the current mission, rally points or geofence plan (a GCS can use this checksum to determine if it has a matching plan definition).
+        This message must be broadcast following any change to a plan (immediately after the MISSION_ACK that completes the plan upload sequence).
+        It may also be requested using MAV_CMD_REQUEST_MESSAGE, where param 2 indicates the plan type for which the hash is required.
+        The checksum must be calculated on the autopilot, but may also be calculated by the GCS.
+        The checksum uses the same CRC32 algorithm as MAVLink FTP (https://mavlink.io/en/services/ftp.html#crc32-implementation).
+        It is run over each item in the plan in seq order (excluding the home location if present in the plan), and covers the following fields (in order):
+        frame, command, autocontinue, param1, param2, param3, param4, param5, param6, param7.
+      </description>
+      <field type="uint8_t" name="mission_type" enum="MAV_MISSION_TYPE">Mission type.</field>
+      <field type="uint32_t" name="checksum">CRC32 checksum of current plan for specified type.</field>
+    </message>
+  </messages>
+</mavlink>