Interfaces and namespaces

New tests In exstension namespace 
```php
namespace Test;
```
https://github.com/zaets28rus/zephir/commit/94621448fbe6cb6cab793f59ae54be6f8b32cc83#diff-54b5d353e050d4d9daacb527a88bb093R2
https://github.com/zaets28rus/zephir/commit/94621448fbe6cb6cab793f59ae54be6f8b32cc83#diff-f82dcc6b8417923856d78de747fcafb1R2

Old test
https://github.com/zaets28rus/zephir/blob/implement_interface_fix_namespaces/test/testinterface.zep#L2
Internal interface from global namespace
https://github.com/zaets28rus/zephir/blob/implement_interface_fix_namespaces/test/testinterface.zep

In namespace use to get another interface from current exstension by slashed on global path
```php
namespace Test\Oo;
```
https://github.com/zaets28rus/zephir/commit/94621448fbe6cb6cab793f59ae54be6f8b32cc83#diff-9d58d3d234cc44ac615342d8f4725428R2