Cleanup fancy pointer rebinding in list using __rebind_pointer.

Currently we need an #ifdef branch every time we use pointer traits to rebind a pointer because
it is done differently in C++11 and C++03. This patch introduces the __rebind_pointer utility to
clean this up. 

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@245802 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed