Add 'previous declaration is here' note for param redefinition 
errors, e.g.:

t.c:1:21: error: redefinition of parameter 'x'
int test(int x, int x);
                    ^
t.c:1:14: note: previous declaration is here
int test(int x, int x);
             ^



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@96769 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/arg-duplicate.c b/test/Sema/arg-duplicate.c
index ca091eb..feeb458 100644
--- a/test/Sema/arg-duplicate.c
+++ b/test/Sema/arg-duplicate.c
@@ -2,7 +2,8 @@
 
 int f3(y, x, 
        x)          // expected-error {{redefinition of parameter}}
-  int y, x, 
+  int y, 
+      x,           // expected-note {{previous declaration is here}}
       x;           // expected-error {{redefinition of parameter}}
 {
   return x + y;