plugins types CHANGE compare function callback

The function now has a new context parameter that may be needed when
getting the canonical value. Type API version number has increased.
diff --git a/src/validation.c b/src/validation.c
index 93a79c7..74653a7 100644
--- a/src/validation.c
+++ b/src/validation.c
@@ -1173,7 +1173,7 @@
                 val2 = slist->uniques[u][v]->dflt;
             }
 
-            if (!val1 || !val2 || val1->realtype->plugin->compare(val1, val2)) {
+            if (!val1 || !val2 || val1->realtype->plugin->compare(ctx, val1, val2)) {
                 /* values differ or either one is not set */
                 break;
             }