Defines some undefined grob properties, grob objects, and music properties.

Defines some undefined grob properties, grob objects, and music properties.

Undefined properties as well as properties without interfaces may
cause memory leaks in LilyPond.  While this issue has to be investigated
further, defining these properties makes the code easier to read and may
lead to less memory leaks, which may in turn speed up batch processing
of .ly files (like the regtests).