[ASTImporter] Lookup SearchName instead of Name

When the SearchName is already calculated we should use that for the lookup.

Patch by Peter Szecsi!

Differential Revision: https://reviews.llvm.org/D30877

llvm-svn: 299354
diff --git a/clang/test/ASTMerge/struct/Inputs/struct2.c b/clang/test/ASTMerge/struct/Inputs/struct2.c
index 4b43df7..7fe17a5 100644
--- a/clang/test/ASTMerge/struct/Inputs/struct2.c
+++ b/clang/test/ASTMerge/struct/Inputs/struct2.c
@@ -58,3 +58,19 @@
   int i;
   float f;
 } x11;
+
+// Matches
+typedef struct {
+  int i;
+  float f;
+} S12;
+
+S12 x12;
+
+// Mismatch
+typedef struct {
+  int i; // Mismatch here.
+  float f;
+} S13;
+
+S13 x13;