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/support/min_allocator.h

@@ -11,6 +11,9 @@
 #define MIN_ALLOCATOR_H
 
 #include <cstddef>
+#include <cstdlib>
+#include <cstddef>
+#include <cassert>
 
 #include "test_macros.h"
 
@@ -39,6 +42,57 @@ public:
     friend bool operator!=(bare_allocator x, bare_allocator y) {return !(x == y);}
 };
 
+struct malloc_allocator_base {
+    static size_t alloc_count;
+    static size_t dealloc_count;
+    static bool disable_default_constructor;
+
+    static size_t outstanding_alloc() {
+      assert(alloc_count >= dealloc_count);
+      return (alloc_count - dealloc_count);
+    }
+
+    static void reset() {
+        assert(outstanding_alloc() == 0);
+        disable_default_constructor = false;
+        alloc_count = 0;
+        dealloc_count = 0;
+    }
+};
+
+
+size_t malloc_allocator_base::alloc_count = 0;
+size_t malloc_allocator_base::dealloc_count = 0;
+bool malloc_allocator_base::disable_default_constructor = false;
+
+
+template <class T>
+class malloc_allocator : public malloc_allocator_base
+{
+public:
+    typedef T value_type;
+
+    malloc_allocator() TEST_NOEXCEPT { assert(!disable_default_constructor); }
+
+    template <class U>
+    malloc_allocator(malloc_allocator<U>) TEST_NOEXCEPT {}
+
+    T* allocate(std::size_t n)
+    {
+        ++alloc_count;
+        return static_cast<T*>(std::malloc(n*sizeof(T)));
+    }
+
+    void deallocate(T* p, std::size_t)
+    {
+        ++dealloc_count;
+        std::free(static_cast<void*>(p));
+    }
+
+    friend bool operator==(malloc_allocator, malloc_allocator) {return true;}
+    friend bool operator!=(malloc_allocator x, malloc_allocator y) {return !(x == y);}
+};
+
 
 #if TEST_STD_VER >= 11