anchor.diff:  { lib, stdenv
   , fetchurl
  -, fetchpatch
   , pkg-config
   , vala
   , gobject-introspection
   , gtk-doc
  -, docbook_xsl
  +, docbook-xsl-nons
   , docbook_xml_dtd_43
   , glib
   , babl
  
positive.code: , librsvg
  , lensfun
  , libspiro
  , netsurf
  , pango
  , poly2tri-c
  
negative.code:     librsvg
      lensfun
      libspiro
      maxflow
      netsurf.libnsgif
      pango
      poly2tri-c
  