Fix #12638: allow_url_fopen php.ini setting is boolean

Function url_get( $p_url ) in url_api.php file doesn't work properly
when 'allow_url_fopen' is set to 'Off'. Instead of using a generic
ini_get() call we should instead use the ini_get_boolean() call to get
this PHP configuration value.

Thanks to loginus for reporting this issue and providing this patch.

core/url_api.php

@@ -36,7 +36,7 @@
 function url_get( $p_url ) {
 
 	# Generic PHP call
-	if( ini_get( 'allow_url_fopen' ) ) {
+	if( ini_get_bool( 'allow_url_fopen' ) ) {
 		return @file_get_contents( $p_url );
 	}