Implement merging of namespace-scope declarations across modules, so
that we can merge, for example, two occurrences of

  namespace N { void f(); }

in two disjoint modules.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147780 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Modules/Inputs/namespaces-left.h b/test/Modules/Inputs/namespaces-left.h
index 6835cda..ea2ae2b 100644
--- a/test/Modules/Inputs/namespaces-left.h
+++ b/test/Modules/Inputs/namespaces-left.h
@@ -25,3 +25,15 @@
 namespace N7 {
   int &f(int);
 }
+
+namespace N8 {
+  int &f(int);
+}
+
+namespace N9 {
+  int &f(int);
+}
+
+namespace N10 {
+  int &f(int);
+}