pw_minimal_cpp_stdlib: Extremely limited C++ lib

pw_minimal_cpp_stdlib is an extremely limited, non-standard
implementation of the C++ Standard Library. It requires C++17 and a C
standard library.

Change-Id: I2d0b8d6cf49730e2c746eddf2c4a23308af1eb6a
diff --git a/pw_minimal_cpp_stdlib/public/internal/cstdarg.h b/pw_minimal_cpp_stdlib/public/internal/cstdarg.h
new file mode 100644
index 0000000..8d31c67
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+++ b/pw_minimal_cpp_stdlib/public/internal/cstdarg.h
@@ -0,0 +1,22 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include <stdarg.h>
+
+namespace std {
+
+using ::va_list;
+
+}  // namespace std