Fix PR22000. __bit_iterator::move_backwards. Also make a note that __bit_iterator
is quite underrepresented in the libc++ tests suite.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@224723 91177308-0d34-0410-b5e6-96231b3b80d8

include/__bit_reference

diff --git a/include/__bit_reference b/include/__bit_reference
index d9ebfbe..4938f44 100644
--- a/include/__bit_reference
+++ b/include/__bit_reference
@@ -705,7 +705,7 @@
 __bit_iterator<_Cp, false>
 move_backward(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
 {
-    return _VSTD::copy(__first, __last, __result);
+    return _VSTD::copy_backward(__first, __last, __result);
 }
 
 // swap_ranges