all lines of the same type must have language / orthographies

If a line type appears multiple times in an interlinear gloss schema, each line must have its language / orthography specified.

**bad**
```
\txn    hujambo dunia
\tln    Hello world.
\tln-es Hola mundo.
```

**good**
```
\txn    hujambo dunia
\tln-en Hello world.
\tln-es Hola mundo.
```