Log Message:
For the sake of graphics/cairo, which derives the libXrender feature
set from the renderproto version, pick a package with an older version
(renderproto9) for anything < netbsd-5.

This change gets the selection criteria right, and also points the
renderproto9 package to renderproto's builtin.mk, avoiding Xrender
breakage.

Fixes pkg/43969 and should probably be pulled up.