Currently, when the coordIndex attribute of an IndexedLineSet contains a polyline with > 2 indices, X3DGeoHelper::coordIdx_str2faces_arr() will incorrectly determine the primitive type to be aiPrimitiveType_TRIANGLE or aiPrimitiveType_POLYGON instead of aiPrimitiveType_LINE. To fix this, this commit adds functions to explicitly handle an IndexedLineSet. Fixes #3101