Add missing return statements in C++03 std::function

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@238803 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__functional_03 b/include/__functional_03
index 785a275..f048ea3 100644
--- a/include/__functional_03
+++ b/include/__functional_03
@@ -825,6 +825,7 @@
     else if (__f_)
         __f_->destroy_deallocate();
     __f_ = 0;
+    return *this;
 }
 
 template<class _Rp>
@@ -1121,6 +1122,7 @@
     else if (__f_)
         __f_->destroy_deallocate();
     __f_ = 0;
+    return *this;
 }
 
 template<class _Rp, class _A0>
@@ -1417,6 +1419,7 @@
     else if (__f_)
         __f_->destroy_deallocate();
     __f_ = 0;
+    return *this;
 }
 
 template<class _Rp, class _A0, class _A1>
@@ -1713,6 +1716,7 @@
     else if (__f_)
         __f_->destroy_deallocate();
     __f_ = 0;
+    return *this;
 }
 
 template<class _Rp, class _A0, class _A1, class _A2>