A node for drawing a TeX expansion (or any char-positioned text). The data are
stored as an array of struct tex_glyph.
It supports the object interface, the node interface and the composite interface.
struct vcl_tex_layout * vcl_tex_layout_new (uns copy,
struct tex_glyph *glyphs, uns glyphs_cnt,
const struct geom_rectangle *bbox)
Creates a TeX-layout. The glyph array is given by
glyphs and its size is glyph_cnt. If copy is true,
then the glyph array is copied, otherwise a pointer is taken
(and the TeX-layout is not responsible for freeing it during the destroying).
*bbox is the bounding box of the entire TeX-layout (in local coords).