lib/mempcpy.[ch]: Remove our definition of mempcpy(3)

It is provided by glibc, musl, and FreeBSD.

Reported-by: Sam James <sam@gentoo.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

configure.ac

@@ -47,7 +47,7 @@ AC_CHECK_HEADER([shadow.h],,[AC_MSG_ERROR([You need a libc with shadow.h])])
 
 AC_CHECK_FUNCS(arc4random_buf futimes \
 	getentropy getrandom getspnam getusershell \
-	initgroups lckpwdf lutimes mempcpy \
+	initgroups lckpwdf lutimes \
 	setgroups updwtmp updwtmpx innetgr \
 	getspnam_r \
 	rpmatch \

lib/Makefile.am

@@ -84,8 +84,6 @@ libshadow_la_SOURCES = \
 	lockpw.c \
 	loginprompt.c \
 	mail.c \
-	mempcpy.c \
-	mempcpy.h \
 	memzero.c \
 	memzero.h \
 	motd.c \

lib/mempcpy.c

@@ -1,23 +0,0 @@
-/*
- * SPDX-FileCopyrightText:  2023, Alejandro Colomar <alx@kernel.org>
- *
- * SPDX-License-Identifier:  BSD-3-Clause
- */
-
-
-#include <config.h>
-
-#if !defined(HAVE_MEMPCPY)
-
-#ident "$Id$"
-
-#include "mempcpy.h"
-
-#include <stddef.h>
-
-
-extern inline void *mempcpy(void *restrict dst, const void *restrict src,
-    size_t n);
-
-
-#endif

lib/mempcpy.h

@@ -1,31 +0,0 @@
-/*
- * SPDX-FileCopyrightText:  2023, Alejandro Colomar <alx@kernel.org>
- *
- * SPDX-License-Identifier:  BSD-3-Clause
- */
-
-
-#ifndef SHADOW_INCLUDE_LIB_MEMPCPY_H_
-#define SHADOW_INCLUDE_LIB_MEMPCPY_H_
-
-
-#include <config.h>
-
-#if !defined(HAVE_MEMPCPY)
-
-#include <stddef.h>
-#include <string.h>
-
-
-inline void *mempcpy(void *restrict dst, const void *restrict src, size_t n);
-
-
-inline void *
-mempcpy(void *restrict dst, const void *restrict src, size_t n)
-{
-	return memcpy(dst, src, n) + n;
-}
-
-
-#endif  // !HAVE_MEMPCPY
-#endif  // include guard

lib/stpecpy.h

@@ -17,8 +17,6 @@
 #include <stddef.h>
 #include <string.h>
 
-#include "mempcpy.h"
-
 
 inline char *stpecpy(char *dst, char *end, const char *restrict src);
 

lib/zustr2stp.h

@@ -14,7 +14,6 @@
 #include <stddef.h>
 #include <string.h>
 
-#include "mempcpy.h"
 #include "must_be.h"
 #include "sizeof.h"