Add Filesystem TS -- Complete

Add the completed std::experimental::filesystem implementation and tests.
The implementation supports C++11 or newer.

The TS is built as part of 'libc++experimental.a'. Users of the TS need to
manually link this library. Building and testing the TS can be disabled using
the CMake option '-DLIBCXX_ENABLE_FILESYSTEM=OFF'.

Currently 'libc++experimental.a' is not installed by default. To turn on the
installation of the library use '-DLIBCXX_INSTALL_EXPERIMENTAL_LIBRARY=ON'.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@273034 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/experimental/filesystem/fs.enum/enum.perms.pass.cpp

@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <experimental/filesystem>
+
+// enum class perms;
+
+#include <experimental/filesystem>
+#include <type_traits>
+#include <cassert>
+#include <sys/stat.h>
+
+#include "test_macros.h"
+#include "check_bitmask_types.hpp"
+
+namespace fs = std::experimental::filesystem;
+
+constexpr fs::perms ME(int val) { return static_cast<fs::perms>(val); }
+
+int main() {
+  typedef fs::perms E;
+  static_assert(std::is_enum<E>::value, "");
+
+  // Check that E is a scoped enum by checking for conversions.
+  typedef std::underlying_type<E>::type UT;
+  static_assert(!std::is_convertible<E, UT>::value, "");
+
+  static_assert(std::is_same<UT, unsigned >::value, ""); // Implementation detail
+
+  typedef check_bitmask_type<E, E::group_all, E::owner_all> BitmaskTester;
+  assert(BitmaskTester::check());
+
+  static_assert(
+        E::none         == ME(0) &&
+
+        E::owner_read   == ME(0400) &&
+        E::owner_write  == ME(0200) &&
+        E::owner_exec   == ME(0100) &&
+        E::owner_all    == ME(0700) &&
+
+        E::group_read   == ME(040) &&
+        E::group_write  == ME(020) &&
+        E::group_exec   == ME(010) &&
+        E::group_all    == ME(070) &&
+
+        E::others_read  == ME(04) &&
+        E::others_write == ME(02) &&
+        E::others_exec  == ME(01) &&
+        E::others_all   == ME(07) &&
+        E::all          == ME(0777) &&
+        E::set_uid      == ME(04000) &&
+        E::set_gid      == ME(02000) &&
+        E::sticky_bit   == ME(01000) &&
+        E::mask         == ME(07777) &&
+        E::unknown      == ME(0xFFFF) &&
+        E::add_perms        == ME(0x10000) &&
+        E::remove_perms     == ME(0x20000) &&
+        E::resolve_symlinks == ME(0x40000),
+        "Expected enumeration values do not match");
+}