Adapt compilerplugins to old Clang versions

Change-Id: I91335f1e81e251f0578792517dded9fae239fb61

compilerplugins/clang/compat.hxx

@@ -41,6 +41,15 @@
 // Compatibility wrapper to abstract over (trivial) changes in the Clang API:
 namespace compat {
 
+inline bool isLookupContext(clang::DeclContext const & ctxt) {
+#if (__clang_major__ == 3 && __clang_minor__ > 7) || __clang_major__ > 3
+    return ctxt.isLookupContext();
+#else
+    return !ctxt.isFunctionOrMethod()
+        && ctxt.getDeclKind() != clang::Decl::LinkageSpec;
+#endif
+}
+
 inline bool isExternCContext(clang::DeclContext const & ctxt) {
 #if (__clang_major__ == 3 && __clang_minor__ >= 4) || __clang_major__ > 3
     return ctxt.isExternCContext();

compilerplugins/clang/typecheck.hxx

@@ -12,11 +12,11 @@
 
 #include <cstddef>
 
-#include <iostream>
-
 #include <clang/AST/DeclBase.h>
 #include <clang/AST/Type.h>
 
+#include "compat.hxx"
+
 namespace loplugin {
 
 class NamespaceCheck;
@@ -72,7 +72,7 @@ public:
     TerminalCheck GlobalNamespace() const {
         return TerminalCheck(
             context_ != nullptr
-            && ((context_->isLookupContext()
+            && ((compat::isLookupContext(*context_)
                  ? context_ : context_->getLookupParent())
                 ->isTranslationUnit()));
     }