C++ PATCH for c++/70522 (friend hides name in unnamed namespace)

[Jason Merrill]

cp_binding_level_find_binding_for_name can find a binding for a hidden 
friend declaration, in which case we shouldn't stop looking into 
anonymous namespaces.  This bug blocked the use of N4381 customization 
points.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit 995a41f6f9153cbc4ec713ec645a3edebc408ec2
Author: Jason Merrill <ja...@redhat.com>
Date:   Tue Apr 19 09:11:38 2016 -0400
    	PR c++/70522
    
    	* name-lookup.c (qualified_lookup_using_namespace): Look through
    	hidden names.

diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 89d84d7..b3828c0 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -4647,8 +4647,9 @@ qualified_lookup_using_namespace (tree name, tree scope,
 	    cp_binding_level_find_binding_for_name (NAMESPACE_LEVEL (scope), name);
 	  if (binding)
 	    {
-	      found_here = true;
 	      ambiguous_decl (result, binding, flags);
+	      if (result->type || result->value)
+		found_here = true;
 	    }
 
 	  for (usings = DECL_NAMESPACE_USING (scope); usings;
diff --git a/gcc/testsuite/g++.dg/lookup/friend18.C b/gcc/testsuite/g++.dg/lookup/friend18.C
new file mode 100644
index 0000000..90cd2d7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/lookup/friend18.C
@@ -0,0 +1,15 @@
+// PR c++/70522
+
+namespace A {
+  struct C {
+    friend void i();
+  };
+  namespace {
+    int i;
+  }
+}
+
+int main()
+{
+  return A::i;
+}