Go: Add MaD related extensible predicates.

Author: michaelnebel

go/ql/lib/semmle/go/dataflow/ExternalFlow.qll

@@ -61,6 +61,7 @@
  */
 
 private import go
+private import ExternalFlowExtensions as Extensions
 private import internal.DataFlowPrivate
 private import internal.FlowSummaryImpl::Private::External
 private import internal.FlowSummaryImplSpecific

go/ql/lib/semmle/go/dataflow/ExternalFlowExtensions.qll

@@ -0,0 +1,27 @@
+/**
+ * This module provides extensible predicates for defining MaD models.
+ */
+
+/**
+ * Holds if a source model exists for the given parameters.
+ */
+extensible predicate sourceModel(
+  string package, string type, boolean subtypes, string name, string signature, string ext,
+  string output, string kind, string provenance
+);
+
+/**
+ * Holds if a sink model exists for the given parameters.
+ */
+extensible predicate sinkModel(
+  string package, string type, boolean subtypes, string name, string signature, string ext,
+  string input, string kind, string provenance
+);
+
+/**
+ * Holds if a summary model exists for the given parameters.
+ */
+extensible predicate summaryModel(
+  string package, string type, boolean subtypes, string name, string signature, string ext,
+  string input, string output, string kind, string provenance
+);