Description:
------------
the http wrapper ignores 'header' option in stream_create_context( ) if the value is not given as a simple array; neither a string nor a map (e.g. array('X-My-Header' => 'test')) will cause the additional headers to be sent.

Reproduce code:
---------------
// given as string, the header will not be sent
$url = 'http://protectedstuff.com';
$auth = base64_encode('user:password');
$header = "Authorization: Basic $auth";
$opts = array( 'http' => array ('method'=>'GET',
                                'header'=>$header));
$ctx = stream_context_create($opts);
file_get_contents($url,false,$ctx);

// only if $header is an array, it will be sent
$url = 'http://protectedstuff.com';
$auth = base64_encode('user:password');
$header = array("Authorization: Basic $auth");
$opts = array( 'http' => array ('method'=>'GET',
                                'header'=>$header));
$ctx = stream_context_create($opts);
file_get_contents($url,false,$ctx);

Expected result:
----------------
// In BOTH cases, one would expect the following headers to be sent 
// with the request

GET / HTTP/1.1

User-Agent: PHP/5.2.1

Host: protectedstuff.com

Pragma: no-cache

Accept: */*

Authorization: Basic dXNlcjpwYXNzd29yZA=




Actual result:
--------------
// The first request is sent with the following headers instead

GET / HTTP/1.1

User-Agent: PHP/5.2.1

Host: protectedstuff.com

Pragma: no-cache

Accept: */*



(note that there is no 'Authorization:' header)