NULL if there is no intersection;
a point if the infinite line is tangent to the circle, or NULL
if strict=TRUE and the point is not on the line (segment or half-line);
a list of two points if the circle and the infinite line meet at
two points, when strict=FALSE; if strict=TRUE and the line is
a segment or a half-line, this can return NULL or a single point.
Arguments
circ
a Circle object
line
a Line object
strict
logical, whether to take into account line$extendA and
line$extendB if they are not both TRUE