Use modern name for libtool init macro

Author: NattyNarwhal

configure.ac

@@ -1605,7 +1605,7 @@ AC_PROVIDE_IFELSE([PHP_REQUIRE_CXX], [], [
   undefine([AC_PROG_CXXCPP])
   AC_DEFUN([AC_PROG_CXXCPP], [php_prog_cxxcpp=disabled])
 ])
-AC_PROG_LIBTOOL
+LT_INIT
 
 PHP_SET_LIBTOOL_VARIABLE([--silent])