bpo-45723: Prepare support for autoconf 2.71

``AC_PROG_EGREP`` should be checked explicitly.

``AC_CONFIG_HEADER`` -> ``AC_CONFIG_HEADERS``

``AC_USE_SYSTEM_EXTENSIONS`` must be defined before first use of ``AC_LINK``
or ``AC_COMPILE`` macros.

``STDC_HEADERS`` and ``AC_HEADER_TIME`` are obsolete.

Signed-off-by: Christian Heimes <[email protected]>

Author: tiran

Include/pyport.h

@@ -216,17 +216,10 @@ typedef Py_ssize_t Py_ssize_clean_t;
  * WRAPPER FOR <time.h> and/or <sys/time.h> *
  ********************************************/
 
-#ifdef TIME_WITH_SYS_TIME
-#include <sys/time.h>
-#include <time.h>
-#else /* !TIME_WITH_SYS_TIME */
 #ifdef HAVE_SYS_TIME_H
 #include <sys/time.h>
-#else /* !HAVE_SYS_TIME_H */
+#endif
 #include <time.h>
-#endif /* !HAVE_SYS_TIME_H */
-#endif /* !TIME_WITH_SYS_TIME */
-
 
 /******************************
  * WRAPPER FOR <sys/select.h> *

Misc/NEWS.d/next/Build/2021-11-07-10-45-40.bpo-45723.AreusF.rst

@@ -0,0 +1,2 @@
+``configure.ac`` is now compatible with autoconf 2.71. Deprecated checks
+``STDC_HEADERS`` and ``AC_HEADER_TIME`` have been removed.

Modules/_collectionsmodule.c

@@ -2,12 +2,7 @@
 #include "pycore_call.h"          // _PyObject_CallNoArgs()
 #include "pycore_long.h"          // _PyLong_GetZero()
 #include "structmember.h"         // PyMemberDef
-
-#ifdef STDC_HEADERS
 #include <stddef.h>
-#else
-#include <sys/types.h>            // size_t
-#endif
 
 /*[clinic input]
 module _collections

Modules/arraymodule.c

@@ -13,14 +13,7 @@
 #include "pycore_moduleobject.h"  // _PyModule_GetState()
 #include "structmember.h"         // PyMemberDef
 #include <stddef.h>               // offsetof()
-
-#ifdef STDC_HEADERS
 #include <stddef.h>
-#else /* !STDC_HEADERS */
-#ifdef HAVE_SYS_TYPES_H
-#include <sys/types.h>          /* For size_t */
-#endif /* HAVE_SYS_TYPES_H */
-#endif /* !STDC_HEADERS */
 
 /*[clinic input]
 module array

Objects/listobject.c

@@ -5,12 +5,7 @@
 #include "pycore_interp.h"        // PyInterpreterState.list
 #include "pycore_object.h"        // _PyObject_GC_TRACK()
 #include "pycore_tuple.h"         // _PyTuple_FromArray()
-
-#ifdef STDC_HEADERS
 #include <stddef.h>
-#else
-#include <sys/types.h>          /* For size_t */
-#endif
 
 /*[clinic input]
 class list "PyListObject *" "&PyList_Type"