next TeX improvement

[Werner LEMBERG]

The file music-drawing-routines.ps is no longer written multiple times
to the dvi file; instead, I changed the \lilypondspecial macro to emit

  \special{header=music-drawing-routines.ps}

once.  This tiny change has various benefits:

  . The size of lilypond.dvi shrinks from 1997088 bytes to 1038148
    bytes.

  . The size of lilypond.ps shrinks from 2271072 to 1318716 bytes.

  . TeX no longer needs to know where to find
    music-drawing-routines.ps.

  . Displaying the dvi and the ps file is faster (at least on my system).

AFAIK, all dvi-to-ps converters support the `header=' special.


    Werner