Description:
------------
I'm using iconv (libiconv) 1.13 with PHP 5.3.1 running under Windows 7 and I've noticed two inconsistencies in calls to iconv_mime_encode() and the documentation page for that function, I'm not sure if this is due to errors on the documentations or if the function is buggy:

1) The documentation page states that if 'output-charset' is not passed with the 'preferences' array it will use the value of 'input-charset'. I was not able to reproduce this, 'output-charset' seems to default to 'iconv.internal_encoding', even when 'input-charset' is set in the 'preferences' argument.

2) The first example in the documentation page ($preferences["scheme"] = "Q") doesn't yield the output that the related comment suggests, spaces are encoded as '=20' and not '_'.

Test script:
---------------
<?php

// 1st inconsistency
echo iconv_get_encoding('internal_encoding') . "\n";
echo iconv_mime_encode('Subject', 'Prüfung Prüfung', array('scheme' => 'Q', 'input-charset' => 'UTF-8')) . "\n";
echo iconv_mime_encode('Subject', 'Prüfung Prüfung', array('scheme' => 'Q', 'input-charset' => 'UTF-8', 'output-charset' => 'UTF-8')) . "\n";

// 2nd inconsistency
$preferences = array(
	"scheme" => "Q",
	"input-charset" => "ISO-8859-1",
	"output-charset" => "UTF-8",
	"line-length" => 76,
	"line-break-chars" => "\n",
);

echo iconv_mime_encode("Subject", "Prüfung Prüfung", $preferences) . "\n";

?>

Expected result:
----------------
ISO-8859-1
Subject: =?UTF-8?Q?Pr=C3=BCfung=20Pr=C3=BCfung?=
Subject: =?UTF-8?Q?Pr=C3=BCfung=20Pr=C3=BCfung?=
Subject: =?UTF-8?Q?Pr=C3=BCfung_Pr=C3=BCfung?=

Actual result:
--------------
ISO-8859-1
Subject: =?ISO-8859-1?Q?Pr=FCfung=20Pr=FCfung?=
Subject: =?UTF-8?Q?Pr=C3=BCfung=20Pr=C3=BCfung?=
Subject: =?UTF-8?Q?Pr=C3=83=C2=BCfung=20Pr=C3=83=C2=BCfung?=