[libc++] Replace `#include ""` with `<>` in libcxx/src/. NFCI.
Our best guess is that the two syntaxes should have exactly equivalent
effects, so, let's be consistent with what we do in libcxx/include/.
I've left `#include "include/x.h"` and `#include "../y.h"` alone
because I'm less sure that they're interchangeable, and they aren't
inconsistent with libcxx/include/ because libcxx/include/ never
does that kind of thing.
Also, use the `_LIBCPP_PUSH_MACROS/POP_MACROS` dance for `<__undef_macros>`,
even though it's technically unnecessary in a standalone .cpp file,
just so we have consistently one way to do it.
Differential Revision: https://reviews.llvm.org/D119561
diff --git a/libcxx/src/string.cpp b/libcxx/src/string.cpp
index 3cde2e9..db7d7d5 100644
--- a/libcxx/src/string.cpp
+++ b/libcxx/src/string.cpp
@@ -6,17 +6,17 @@
//
//===----------------------------------------------------------------------===//
-#include "string"
-#include "charconv"
-#include "cstdlib"
-#include "cerrno"
-#include "limits"
-#include "stdexcept"
+#include <__debug>
+#include <cerrno>
+#include <charconv>
+#include <cstdlib>
+#include <limits>
+#include <stdexcept>
#include <stdio.h>
-#include "__debug"
+#include <string>
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
-# include "cwchar"
+# include <cwchar>
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
