MusicXML: Better support for drums

MusicXML: Better support for drums

-) Add the bass drum instrument
-) Ignore notes with the attribute print-object="no". These are
   typically notes that indicate midi output for tremolos and should
   not be printed.
-) Use the Musix_xml_node.message method to print out the warning about
   missing note types. This also prints out where the problem occurs.

Signed-off-by: Reinhold Kainhofer <reinhold@kainhofer.com>