[libc++] Fix directory_iterator compilation on Win32
[libc++] Fix directory_iterator compilation on Win32

This patch fixes some typos and other small errors in
directory_iterator.cpp that prevented this file from being compiled for
Win32.

Patch by Stefan Schmidt <thrimbor.github@gmail.com>!

Differential Revision: https://reviews.llvm.org/D66986

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@370599 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx