Fixed bug #37764

Fixed bug #37764
- Created new abstract class, ReflectionFunctionAbstract implementing Reflector
- Moved all methods from ReflectionFunction (except export, invoke & invokeArgs)
- ReflectionFunction now inherits everything from ReflectionFunctionAbstract
    and implements its own export, invoke & invokeArgs methods
- ReflectionMethod now extends ReflectionFunctionAbstract and implements
    its own export, invoke & invokeArgs methods.
- Removed stdClass typehint from ReflectionClass::isInstance
- Removed stdClass typehint from ReflectionClass::set/getValue