Make renderer-cache really thread-safe this time. Last try was not quite

Make renderer-cache really thread-safe this time. Last try was not quite

2006-11-25  Behdad Esfahbod  <behdad@gnome.org>

        * pango/pangocairo-render.c (acquire_renderer), (release_renderer),
        (_pango_cairo_do_glyph_string), (_pango_cairo_do_layout_line),
        (_pango_cairo_do_layout):  Make renderer-cache really thread-safe this
        time.  Last try was not quite thread-safe theoretically, because
        pointer assignments are not necessarily atomic on some archs.  Anyway,
        this one should do it.