Allow x-amz headers in $requestHeaders param.

With this, custom headers like
‘x-amz-server-side-encryption-customer-algorithm’ will work.

S3.php

@@ -642,7 +642,8 @@ public static function putObject($input, $bucket, $uri, $acl = self::ACL_PRIVATE
 
 		// Custom request headers (Content-Type, Content-Disposition, Content-Encoding)
 		if (is_array($requestHeaders))
-			foreach ($requestHeaders as $h => $v) $rest->setHeader($h, $v);
+			foreach ($requestHeaders as $h => $v)
+				strpos($h, 'x-amz-') === 0 ? $rest->setAmzHeader($h, $v) : $rest->setHeader($h, $v);
 		elseif (is_string($requestHeaders)) // Support for legacy contentType parameter
 			$input['type'] = $requestHeaders;
 
@@ -797,7 +798,8 @@ public static function copyObject($srcBucket, $srcUri, $bucket, $uri, $acl = sel
 	{
 		$rest = new S3Request('PUT', $bucket, $uri, self::$endpoint);
 		$rest->setHeader('Content-Length', 0);
-		foreach ($requestHeaders as $h => $v) $rest->setHeader($h, $v);
+		foreach ($requestHeaders as $h => $v)
+				strpos($h, 'x-amz-') === 0 ? $rest->setAmzHeader($h, $v) : $rest->setHeader($h, $v);
 		foreach ($metaHeaders as $h => $v) $rest->setAmzHeader('x-amz-meta-'.$h, $v);
 		if ($storageClass !== self::STORAGE_CLASS_STANDARD) // Storage class
 			$rest->setAmzHeader('x-amz-storage-class', $storageClass);