If a thread is cancelled while it holds a mutex, other threads waiting for
the mutex will never be woken, even if destroying the mutex, thus
leading to a deadlock.

Better just make the thread loops have a proper exit case than risking
the tricky semantic of pthread_cancel.

This reverts commit 6042eb8d1e.

The change causes an issue with `pt-BR` and possibly other languages
and voices.

Fixes #555.

if this was not set in spelling rules already

as phoneme set for both is the same, rename phoneme translation file to in

otherwise it can't be distinguished from D