[feature] support multiple lines of matcher

See this model:

```ini
[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[role_definition]
g = _, _
g2 = _, _

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = g(r.sub, p.sub) && (r.obj == p.obj || g2(r.obj, p.obj)) && r.act == p.act
```

The matcher can be:

```
m = {
let role_match = g(r.sub, p.sub);

let obj_direct_match = r.obj == p.obj;
let obj_inherit_match = g2(r.obj, p.obj);
let obj_match = obj_direct_match || obj_inherit_match;

let act_match = r.act == p.act;

return role_match && obj_match && act_match
}
```

or:

```
m = {
let role_match = g(r.sub, p.sub);
if !role_match {
return false;
}

if r.act != p.act {
return false;
}

if r.obj == p.obj {
return true;
}

if g2(r.obj, p.obj) {
return true;
}

return false;
}
```