Returns the lines of the layout as a list.
This is a faster alternative to Layout.getLines,
but the user is not expected
to modify the contents of the lines (glyphs, glyph widths, etc.).
a GSList containing
the lines in the layout. This points to internal data of the gtk.Layout and
must be used with care. It will become invalid on any change to the layout's
text or properties. No changes should be made to the lines.