v.in.dxf3d bug fix

hi, all.

v.in.dxf3d bug fix is available from:

ftp://geni.knu.ac.kr/pub/geni/patch/grass/grass5.0beta8-CVS/patch.rt6.gz

README.rt6
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1. v.in.dxf3d cannot label two VERTEX polyline because the parser searches for
   the third VERTEX and then write info to a file.
   Now, the parser searches for " 0\n".

Regards,
Huidae Cho