CLEANUP: ebtree: remove 4-year old harmless typo in duplicates insertion code

(from ebtree 6.0.7)

This typo has been there since we introduced duplicates. A "struct eb_troot *"
which apparently the compiler doesn't complain about while it is never declared
anywhere. Amazing...

(cherry picked from commit 2879648db5d32cf009ae571cb0e8e1df75152281)
diff --git a/ebtree/ebtree.h b/ebtree/ebtree.h
index 2ec9dc7..eb7d021 100644
--- a/ebtree/ebtree.h
+++ b/ebtree/ebtree.h
@@ -456,9 +456,9 @@
 {
 	struct eb_node *head = sub;
 	
-	struct eb_troot *new_left = eb_dotag(&new->branches, EB_LEFT);
-	struct eb_troot *new_rght = eb_dotag(&new->branches, EB_RGHT);
-	struct eb_troot *new_leaf = eb_dotag(&new->branches, EB_LEAF);
+	eb_troot_t *new_left = eb_dotag(&new->branches, EB_LEFT);
+	eb_troot_t *new_rght = eb_dotag(&new->branches, EB_RGHT);
+	eb_troot_t *new_leaf = eb_dotag(&new->branches, EB_LEAF);
 
 	/* first, identify the deepest hole on the right branch */
 	while (eb_gettag(head->branches.b[EB_RGHT]) != EB_LEAF) {