Revert "Problems if the json-message contains special characters [...]"

This reverts commit 7968aef.

As per the JSON specification in RFC 7159 section 8.1, "JSON text
SHALL be encoded in UTF-8, UTF-16, or UTF-32". [1]

It is therefore incorrect to apply utf8_encode() function to the data
received from the server since it is already in Unicode by definition.

Fixes #20350

[1] https://tools.ietf.org/html/rfc7159#section-8.1

Conflicts:
	core/json_api.php
	library/adodb
	library/disposable
	library/ezc/Base
	library/ezc/Graph
	library/phpmailer

core/json_api.php

@@ -41,7 +41,7 @@
  */
 function json_url( $p_url, $p_member = null ) {
 	$t_data = url_get( $p_url );
-	$t_json = json_decode( utf8_encode( $t_data ) );
+	$t_json = json_decode( $t_data );
 
 	if( is_null( $p_member ) ) {
 		return $t_json;