Drop the requirement for the entry points to WordPress to be parsable by PHP4.

Previously we ensured that the entry points to WordPress were parsable by PHP4 in order to display a friendly not-supported-php error message.
However, for the last two years the main entry points have not actually parsed, and we've only added extra parse errors since it last worked in 3.9, so it's time we just remove this 'feature'.
The PHP version checks are still there for PHP 5.0/5.1, and so it's inplace when we eventually drop PHP 5.2 support.

See #29489.


git-svn-id: https://develop.svn.wordpress.org/trunk@38899 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/setup-config.php

@@ -5,8 +5,6 @@
  * The permissions for the base directory must allow for writing files in order
  * for the wp-config.php to be created using this page.
  *
- * @internal This file must be parsable by PHP4.
- *
  * @package WordPress
  * @subpackage Administration
  */
@@ -316,7 +314,6 @@ switch($step) {
 	}
 
 	$key = 0;
-	// Not a PHP5-style by-reference foreach, as this file must be parseable by PHP4.
 	foreach ( $config_file as $line_num => $line ) {
 		if ( '$table_prefix  =' == substr( $line, 0, 16 ) ) {
 			$config_file[ $line_num ] = '$table_prefix  = \'' . addcslashes( $prefix, "\\'" ) . "';\r\n";