Log Message:
Update to 1.6.4 from 1.6.3.  pkgsrc changes:

  upstream has provided a way to fetch the distfile with a URL that
  can be constructed by pkgsrc

Upstream changes:

  *  Experimental support for the build tool waf.

  * Fix test failures when compiling with -O0. See r631.

  * Ensure that conversions from double to int are performed
    correctly. Fixes for ticket31.

  * Clarify what gtk_image_view_get_draw_rect() and
    gtk_image_view_get_viewport() returns when the view is not
    allocated.