MissionPlanner build ignores the .xml files in ExtLibs/Mavlink/message_definitions/

I am trying to test the addition of a new MAVLINK message to common.xml in both MissionPlanner and ArduCopter. With ArduCopter, it was trivially easy; just added the new message to modules/mavlink/message_definitions/v1.0/common.xml and rebuilt copter using waf, and everything worked flawlessly. When I made the same mods to ExtLibs/Mavlink/message_definitions/common.xml, it was completely ignored! In fact, I renamed all of the .xml files in the message_definitions folder, and MAVLink.dll was still built, probably because the stuff that is supposed to be generated from the .xml files was already there. Am I looking in the wrong place? I’d truly appreciate any help in resolving this issue. Thanks in advance.

I executed ./ExtLibs/Mavlink/regenerate.bat and that used the updated common.xml and generated new .cs files and .dll ! This seems to have solved the main issue.