Log Message:
Re-implement check for older native X11 systems to use renderproto9.

(For making the unreasonable assumption that BUILTIN_X11_TYPE.native on
a native NetBSD xorg system would be "xorg" I am awarded the Fail In
Technology prize of... a full set of "Synergy on P/OS" install media.
- - The correct answer was of course "unknown".)

Also make the test a little more robust, if not more attractive.

As further spice for this particular value equation; earlier this week I
switched the only platform I had for which this was relevant (OS X 10.4)
to modular X11, but I take solace from the fact this should make the lives
of those building x11 apps from current pkgsrc on netbsd-4 no less painful
than they were before...