Skip transparent contexts when looking for using directives in name lookup.

Fixes the bootstrap regression I introduced in r179067.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179079 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index ebe2894..b631d8b 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -962,8 +962,12 @@
           // If we haven't handled using directives yet, do so now.
           if (!VisitedUsingDirectives) {
             // Add using directives from this context up to the top level.
-            for (DeclContext *UCtx = Ctx; UCtx; UCtx = UCtx->getParent())
+            for (DeclContext *UCtx = Ctx; UCtx; UCtx = UCtx->getParent()) {
+              if (UCtx->isTransparentContext())
+                continue;
+
               UDirs.visit(UCtx, UCtx);
+            }
 
             // Find the innermost file scope, so we can add using directives
             // from local scopes.