[4.2] Model : take booleans in consideration in originalIsNumericallyEquivalent

Take boolean in consideration in originalIsNumericallyEquivalent() and tries to solve https://github.com/laravel/framework/issues/4675

So that booleans can also be equivalent:
```php
true
1.0
1
'1'
'1.000'
// are equivalent and...

false
0.0
0
'0'
'0.000'
// are also equivalent
```