Bug 726495 - "Text to path" delivers a path offset from the text

In gimp_text_layout_render() do a cairo_save/restore() around drawing
the (possibly offset and transformed) text, so we can later get the
rendered path from cairo_copy_path() relative to the original coords
and not relative to the offset and transformed coords.

(cherry picked from commit 7257574b9369a60495a865341ef2a44c1186934b)