Description:
------------
Documentation tells that SplTempFileObject::__construct() inherits SplFileObject::__construct, but this isn't true since the constructor is overwrited in the class:

```
/* Methods */
public __construct ([ int $max_memory ] )

/* Inherited methods */
public SplFileObject::__construct ( string $filename [, string $open_mode = "r" [, bool $use_include_path = false [, resource $context ]]] )
```

Since there is no access to parent's constructor, there is no way to specify the open mode for SplTempFileObject.

Test script:
---------------
$file = new \SplTempFileObject('php://temp', 'a+');
$file->fwrite(file_get_contents($filePath));
$file->fflush();

Expected result:
----------------
$file->isReadable(); // I would expect this to return true, but the open mode is always "w" and I haven't a way to change it.

Actual result:
--------------
```
RuntimeException: SplTempFileObject::__construct() expects at most 1 parameter, 2 given
```