MINOR: pattern: add function to lookup a specific entry in pattern list

This is used to dynamically delete or update map entry.
diff --git a/include/proto/pattern.h b/include/proto/pattern.h
index 8c9c1c7..080b062 100644
--- a/include/proto/pattern.h
+++ b/include/proto/pattern.h
@@ -151,5 +151,7 @@
 void pattern_free(struct pattern *pat);
 void pattern_prune_expr(struct pattern_expr *expr);
 void pattern_init_expr(struct pattern_expr *expr);
+int pattern_lookup(const char *args, struct pattern_expr *expr, struct pattern **pat_elt, struct pat_idx_elt **idx_elt, char **err);
+
 
 #endif