Revert r249929 ("Split <string.h> out of <cstring>").

This change caused problems when building code like povray that:
a) uses 'using namespace std;'
b) is built on an environment where the C library provides the "wrong"
   (non-const-correct) interface for the str* functions
c) makes an unqualified call to one of those str* functions

A patch is out for review to add a facility to fix this (and to give the
correct signatures for these functions whenever possible, even when the C
library does not do so). This revert is expected to be temporary.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@251665 91177308-0d34-0410-b5e6-96231b3b80d8

include/string.h

@@ -1,63 +0,0 @@
-// -*- C++ -*-
-//===--------------------------- string.h ---------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef _LIBCPP_STRING_H
-#define _LIBCPP_STRING_H
-
-/*
-    string.h synopsis
-
-Macros:
-
-    NULL
-
-Types:
-
-    size_t
-
-void* memcpy(void* restrict s1, const void* restrict s2, size_t n);
-void* memmove(void* s1, const void* s2, size_t n);
-char* strcpy (char* restrict s1, const char* restrict s2);
-char* strncpy(char* restrict s1, const char* restrict s2, size_t n);
-char* strcat (char* restrict s1, const char* restrict s2);
-char* strncat(char* restrict s1, const char* restrict s2, size_t n);
-int memcmp(const void* s1, const void* s2, size_t n);
-int strcmp (const char* s1, const char* s2);
-int strncmp(const char* s1, const char* s2, size_t n);
-int strcoll(const char* s1, const char* s2);
-size_t strxfrm(char* restrict s1, const char* restrict s2, size_t n);
-const void* memchr(const void* s, int c, size_t n);
-      void* memchr(      void* s, int c, size_t n);
-const char* strchr(const char* s, int c);
-      char* strchr(      char* s, int c);
-size_t strcspn(const char* s1, const char* s2);
-const char* strpbrk(const char* s1, const char* s2);
-      char* strpbrk(      char* s1, const char* s2);
-const char* strrchr(const char* s, int c);
-      char* strrchr(      char* s, int c);
-size_t strspn(const char* s1, const char* s2);
-const char* strstr(const char* s1, const char* s2);
-      char* strstr(      char* s1, const char* s2);
-char* strtok(char* restrict s1, const char* restrict s2);
-void* memset(void* s, int c, size_t n);
-char* strerror(int errnum);
-size_t strlen(const char* s);
-
-*/
-
-#include <__config>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
-#endif
-
-#include_next <string.h>
-
-#endif  // _LIBCPP_STRING_H