More work on cleaning up the xml outputter for msvcbuild.

Change-Id: I3564ee9d0fec5ac9ef2915d88bcb455680412172
Reviewed-on: http://www.matthewh.me/gerrit/43
Reviewed-by: Matthew Hoggan <mehoggan@gmail.com>
Tested-by: Matthew Hoggan <mehoggan@gmail.com>