makefile: move pdlibc to extlib, add C++ stub standard headers

It now kind of compiles with x86_64-elf gcc (does not link though)

libstd/README

@@ -0,0 +1,5 @@
+
+This folder is in place for the most standard headers not in the PDLibC extlib.
+
+Mostly for C++ standard headers.
+

libstd/__cpp_config.hpp

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+#pragma once
+
+
+#if __cplusplus >= 201103L
+#define __CXX11
+#endif
+#if __cplusplus >= 201402L
+#define __CXX14
+#endif
+#if __cplusplus >= 201703L
+#define __CXX17
+#endif
+#if __cplusplus >= 202002L
+#define __CXX20
+#endif
+
+
+#ifdef __CXX11
+#define __NOTHROW noexcept
+#define __NOTHROW_SINCECXX11 __NOTHROW
+#else
+#define __NOTHROW throw()
+#define __NOTHROW_SINCECXX11
+#endif
+

libstd/exception

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+#pragma once
+#include <__cpp_config.hpp>
+
+extern "C++" {
+namespace std {
+
+
+class exception {
+public:
+	exception() __NOTHROW {}
+#ifdef __CXX11
+	exception(const exception &) = default;
+	exception &operator=(const exception &) = default;
+	exception(exception &&)                 = default;
+	exception &operator=(exception &&) = default;
+#endif
+
+	virtual const char *what() const __NOTHROW { return "std::exception"; };
+};
+
+
+} // namespace std
+}

libstd/new

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+#pragma once
+#include <__cpp_config.hpp>
+
+#include <exception>
+
+extern "C++" {
+namespace std {
+
+
+class bad_alloc: public exception {
+public:
+	bad_alloc() __NOTHROW {}
+#ifdef __CXX11
+	bad_alloc(const bad_alloc &) = default;
+	bad_alloc &operator=(const bad_alloc &) = default;
+#endif
+	virtual ~bad_alloc() __NOTHROW {}
+
+	virtual const char *what() const __NOTHROW { return "std::bad_alloc"; }
+};
+
+#ifdef __CXX11
+class bad_array_new_length: public bad_alloc {
+public:
+	bad_array_new_length() __NOTHROW {}
+	virtual ~bad_array_new_length() __NOTHROW {}
+
+	virtual const char *what() const __NOTHROW { return "std::bad_array_new_length"; }
+};
+#endif
+
+
+#ifdef __CXX17
+enum class align_val_t : size_t {};
+#endif
+
+struct nothrow_t {
+#ifdef __CXX11
+	explicit nothrow_t() = default;
+#endif
+};
+extern const nothrow_t nothrow;
+
+
+// new_handler omitted
+
+// new/delete omitted, use memory/memory.hpp
+
+
+} // namespace std
+}