SFINAE __bit_iterator such that it will only get instantiated with a container that has the nested type __storage_type.  This prevents accidental instantiation such as in http://llvm.org/bugs/show_bug.cgi?id=12755.  This fixes http://llvm.org/bugs/show_bug.cgi?id=12755.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@156308 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed