json_encode: implemented JSON_PRETTY_PRINT, json_*: fixed float point encode/decode

[comm644]

Hi!

Please merge this changes for json_encode/decode. and add unit-tests.

1. Implemented JSON_PRETTY_PRINT

test case:

<?php


echo json_encode([
        "object" =>[ 
                "a"=>[
                        "value" => 10,
                        "array" => [10,2,3,4,5]
                ],
                "b"=>[
                        "value" => 10,
                        "array" => [10,2,3,4,5],
                        "strings" => ["some stringA", "some string B"]
                ]
        ]
], JSON_PRETTY_PRINT);

2. Fixed float point encoding decoding when locale not "C"

test case:

<?php

#ifndef KPHP
$locale = 'ru_RU.UTF-8';
setlocale(LC_ALL, $locale);
putenv('LC_ALL=' . $locale);
#endif

$mixed = [
        "value"=> 10.1896
];

$json = json_encode($mixed);


echo "encoded: \n". $json ."\n";

echo "decoded: \n";
print_r( json_decode($json, true) );