Warn about more than the first unused variable when -Werror is set.

To do this, thread DiagnosticErrorTrap's hasUnrecoverableErrorOccurred through
to Scope.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178294 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/warn-unused-variables-werror.c b/test/Sema/warn-unused-variables-werror.c
new file mode 100644
index 0000000..ceaff1b
--- /dev/null
+++ b/test/Sema/warn-unused-variables-werror.c
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -Werror -verify %s
+
+void f() {
+  int i;  // expected-error{{unused}}
+  int j;  // expected-error{{unused}}
+}