Code Modernisation: Remove the SPL autoloader polyfill.

As of PHP 5.3, the SPL extension cannot be disabled, so we no longer need this polyfill.

The file is kept with a `_deprecated_file()` call, to alert any plugins or themes that may be loading it directly.

Props jrf, ayeshrajans.
See #47698, #46630.



git-svn-id: https://develop.svn.wordpress.org/trunk@45637 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/compat.php

@@ -449,16 +449,6 @@ if ( ! function_exists( 'sodium_crypto_box' ) ) {
 	require ABSPATH . WPINC . '/sodium_compat/autoload.php';
 }
 
-/**
- * Polyfill for the SPL autoloader. In PHP 5.2 (but not 5.3 and later), SPL can
- * be disabled, and PHP 7.2 raises notices if the compiler finds an __autoload()
- * function declaration. Function availability is checked here, and the
- * autoloader is included only if necessary.
- */
-if ( ! function_exists( 'spl_autoload_register' ) ) {
-	require_once ABSPATH . WPINC . '/spl-autoload-compat.php';
-}
-
 if ( ! function_exists( 'is_countable' ) ) {
 	/**
 	 * Polyfill for is_countable() function added in PHP 7.3.