v.in.dxf

[Olga Waupotitsch]

MODIFICATIONS to v.in.dxf:
1. v.in.dxf didn't import arcs of negative radius and arcs
where starting angle was greater than ending angle.

2. also v.in.dxf did not check if all polyline points are actual vertices, and
not control frame points for spline.

3. also it ignored bulge factor, which indicates that there should be
not a straight line segment between 2 vertices on polyline, but an
arc parameters of which can be computed from 2 vertex coordinates
plus bulge factor.

make_arc() function needed to be modified to make an arc starting
not from index zero in line points structure, but starting
from given offset, in order to add on arcs to polylines.

Also I made make_arc handle negative radius (clock wise direction)
and situations where start_angle > finish_angle.

I modified add_polyline() to ignore frame control points (case 70:
vertex flag) and to compute arcs when bulge (case 42) is not 0
by computing starting and ending angle , radius, coordinates of
center, and calling make_arc() with the offset into polyline,
instead of just ignoring case 42 and making straight line segments between
all vertices of polyline.


I put the new version on moon (grass/incoming)
Olga