v.in.dxf3d bug fixes

hi,

"v.in.dxf3d dxf=big.dxf lines=123,321" causes Seg faults error.

Bug fix is available from:

ftp://geni.knu.ac.kr/pub/geni/patch/grass/grass5.0beta8-CVS/patch.rt5.gz

README.rt5
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1. v.in.dxf3d with lines option causes Seg faults.
   num of lines can be greater than 3, NUMLINES = 256.

Regards,
Huidae Cho