Assumption about value type causes parsing error

https://github.com/doctrine/annotations/blob/9419fd5b220de184c9501a16ede49a029b94d482/lib/Doctrine/Common/Annotations/DocParser.php#L810

Line #810 is the `elseif (...)` line

if ($type['type'] === 'array') {
// handle the case of a single value
if ( ! is_array($values[$property])) {
$values[$property] = array($values[$property]);
}
// checks if the attribute has array type declaration, such as "array"
if (isset($type['array_type'])) {
foreach ($values[$property] as $item) {
if (gettype($item) !== $type['array_type'] && !$item instanceof $type['array_type']) {
throw AnnotationException::attributeTypeError($property, $originalName, $this->context, 'either a(n) '.$type['array_type'].', or an array of '.$type['array_type'].'s', $item);
}
}
}
} elseif (gettype($values[$property]) !== $type['type'] && !$values[$property] instanceof $type['type']) {
throw AnnotationException::attributeTypeError($property, $originalName, $this->context, 'a(n) '.$type['value'], $values[$property]);
}

Assumes type annotation of value to be done like so:

@var string

However, you could do something like

@var null|string

Because the `elseif()` only does string comparisons, using the latter notation will always fail.

--------------

Small use case

/**
* @var string
* @ORM\Column(name="api_pass", type="text", nullable=false)
* @Encrypted(spices="credential")
*/
protected $apiPass;

Here the `@Encrypted` is custom Annotation. I'll leave all options out of the scope but it's defined like so:

```
/**
* @Annotation
* @Target("PROPERTY")
*/
class Encrypted
{
/**
* @var string
*/
public $spices;

// getters/setters + other options
}
```

However, I would like to define the property like so:

/**
* @var null|string
*/
public $spices;

The first passes, the second fails because an assumption is done that the `@var` declaration always contains just one type.

-------------

P.s. - I've seen comments before about creating a test case, PR and PhpUnit tested code and such. If you have any docs on "how-to" all that, I'll give creating that a shot.