Replace obsolete AC_TRY_FOO with AC_FOO_IFELSE

Autoconf made several macros obsolete including the AC_TRY_COMPILE and
AC_TRY_LINK in 2000 and since Autoconf 2.50:
http://git.savannah.gnu.org/cgit/autoconf.git/tree/ChangeLog.2

These macros should be replaced with the current AC_FOO_IFELSE instead.

It is fairly safe to upgrade and take the recommendation advice of autoconf
upgrade manual since the upgrade should be compatible at least with PHP
versions 5.4 and up, on some systems even with PHP 5.3. PHP versions
from 5.4 to 7.1 require Autoconf 2.59+ and PHP 7.2+ require Autoconf
2.64+.

This patch was created with the help of autoupdate script.

Reference docs:
- https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Obsolete-Macros.html
- https://www.gnu.org/software/autoconf/manual/autoconf-2.59/autoconf.pdf

Author: petk

config.m4

@@ -260,17 +260,15 @@ if test "$PHP_MEMCACHED" != "no"; then
     dnl # Always check if libmemcached was built with SASL support,
     dnl # because it will require sasl.h even if not used here.
     AC_CACHE_CHECK([for libmemcached sasl.h requirement], ac_cv_memc_sasl_support, [
-      AC_TRY_COMPILE(
-        [ #include <libmemcached/memcached.h> ],
-        [
+      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <libmemcached/memcached.h>]], [[
         #if LIBMEMCACHED_WITH_SASL_SUPPORT
           /* yes */
         #else
         #  error "no sasl support"
         #endif
-        ],
-        [ ac_cv_memc_sasl_support="yes" ],
-        [ ac_cv_memc_sasl_support="no" ]
+        ]])],
+        [ac_cv_memc_sasl_support="yes"],
+        [ac_cv_memc_sasl_support="no"]
       )
     ])
 
@@ -304,12 +302,11 @@ if test "$PHP_MEMCACHED" != "no"; then
     LIBS="$LIBS $PHP_LIBMEMCACHED_LIBS"
 
     AC_CACHE_CHECK([whether memcached_exist is defined], ac_cv_have_memcached_exist, [
-      AC_TRY_LINK(
-        [ #include <libmemcached/memcached.h> ],
-        [ memcached_exist (NULL, NULL, 0); ],
-        [ ac_cv_have_memcached_exist="yes" ],
-        [ ac_cv_have_memcached_exist="no" ]
-      )
+      AC_LINK_IFELSE(
+        [AC_LANG_PROGRAM([[#include <libmemcached/memcached.h>]],
+          [[memcached_exist (NULL, NULL, 0);]])],
+          [ac_cv_have_memcached_exist="yes"],
+          [ac_cv_have_memcached_exist="no"])
     ])
 
     CFLAGS="$ORIG_CFLAGS"
@@ -323,12 +320,11 @@ if test "$PHP_MEMCACHED" != "no"; then
     fi
 
     AC_CACHE_CHECK([whether memcached_set_encoding_key is defined], ac_cv_have_memcached_set_encoding_key, [
-      AC_TRY_LINK(
-        [ #include <libmemcached/memcached.h> ],
-        [ memcached_set_encoding_key (NULL, NULL, 0); ],
-        [ ac_cv_have_memcached_set_encoding_key="yes" ],
-        [ ac_cv_have_memcached_set_encoding_key="no" ]
-      )
+      AC_LINK_IFELSE(
+        [AC_LANG_PROGRAM([[#include <libmemcached/memcached.h>]],
+          [[memcached_set_encoding_key (NULL, NULL, 0);]])],
+        [ac_cv_have_memcached_set_encoding_key="yes"],
+        [ac_cv_have_memcached_set_encoding_key="no"])
     ])
 
     CFLAGS="$ORIG_CFLAGS"
@@ -360,13 +356,12 @@ if test "$PHP_MEMCACHED" != "no"; then
       AC_MSG_RESULT([enabled])
 
       AC_CACHE_CHECK([whether libmemcachedprotocol is usable], ac_cv_have_libmemcachedprotocol, [
-        AC_TRY_COMPILE(
-          [ #include <libmemcachedprotocol-0.0/handler.h> ],
-          [ memcached_binary_protocol_callback_st s_test_impl;
+        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <libmemcachedprotocol-0.0/handler.h>]],
+          [[memcached_binary_protocol_callback_st s_test_impl;
             s_test_impl.interface.v1.delete_object = 0;
-          ],
-          [ ac_cv_have_libmemcachedprotocol="yes" ],
-          [ ac_cv_have_libmemcachedprotocol="no" ]
+          ]])],
+          [ac_cv_have_libmemcachedprotocol="yes"],
+          [ac_cv_have_libmemcachedprotocol="no"]
         )
       ])