[libcxx] Move all algorithms into their own headers

This is a fairly mechanical change, it just moves each algorithm into
its own header. This is intended to be a NFC.

This commit re-applies 7ed7d4ccb899, which was reverted in 692d7166f771
because the Modules build got broken. The modules build has now been
fixed, so we're re-committing this.

Differential Revision: https://reviews.llvm.org/D103583

Attribution note
----------------
I'm only committing this. This commit is a mix of D103583, D103330 and
D104171 authored by:

Co-authored-by: Christopher Di Bella <cjdb@google.com>
Co-authored-by: zoecarver <z.zoelec2@gmail.com>

1 files changed, 50 insertions, 0 deletions

diff --git a/libcxx/include/__algorithm/remove.h b/libcxx/include/__algorithm/remove.h
new file mode 100644
index 0000000..f8a6f27
--- /dev/null
+++ b/libcxx/include/__algorithm/remove.h
@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_REMOVE_H
+#define _LIBCPP___ALGORITHM_REMOVE_H
+
+#include <__config>
+#include <__algorithm/find.h>
+#include <utility>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _ForwardIterator, class _Tp>
+_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
+remove(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
+{
+    __first = _VSTD::find(__first, __last, __value_);
+    if (__first != __last)
+    {
+        _ForwardIterator __i = __first;
+        while (++__i != __last)
+        {
+            if (!(*__i == __value_))
+            {
+                *__first = _VSTD::move(*__i);
+                ++__first;
+            }
+        }
+    }
+    return __first;
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ALGORITHM_REMOVE_H