Remove the device-offset testing (-25 cases) for the release.

The reasoning behind the -25 testing is that we want to ensure
that cairo provides translation invariance. However, for
many vector backends we use external rasterizers that don't
necessarily provide that translation invariance.

So this testing makes a bunch of failures appear that we don't
really care about, (and we don't even have a mechanism to turn
them off with custom reference images). For the release, I'm
just turning this off.

After the release, I plan to turn this back on, and then we could
fix this by ensuring that the vector output itself is unaffected
by a device offset, or by moving away from external rasterizers,
(see Chris's micro-gs work to test PostScript with cairo-based
rasterization).

test/cairo-test.c

@@ -78,7 +78,7 @@ static const char *fail_face = "", *normal_face = "";
 #define CAIRO_TEST_REF_SUFFIX "-ref.png"
 #define CAIRO_TEST_DIFF_SUFFIX "-diff.png"
 
-#define NUM_DEVICE_OFFSETS 2
+#define NUM_DEVICE_OFFSETS 1
 
 static const char *vector_ignored_tests[] = {
     /* We can't match the results of tests that depend on