Consider default exceptions as possibly thrown exceptions

[marcospassos]

This PR fix #57 by suppressing warnings about unused exception configurated through methodThrowTypeDeclarations, better illustrated below:

class Example {
        /**
	 * @throws CheckedException
	 */
	private function methodWithDefaultThrowType(callable $callable): void // error: Unused @throws CheckedException annotation
	{
		$callable();
	}
}

exceptionRules:
     methodThrowTypeDeclarations:
        Example:
            methodWithDefaultThrowType: [FooException]