Use #define for imports

This simple change will allow to use repository as git submodule without much trouble; example:

* Repository added as submodule to scripts/utils/fonline-json/
* scripts/utils/json.fos
```
#include "fonline-json/src/json.fos
```
* scripts/utils/json_h.fos
```
#define JSON_MODULE "utils/json"
#include "fonline-json/src/json_h.fos"
```
* scripts.cfg entry: @ [target] module utils/json

Configuration like that will
* allow using repository as submodule without need to manually fix imports
* allow to use own name for module without need to edit source
* create .fosb/.fosp files inside scripts/utils/, leaving submodule directory clean