Remove the second indocumented argument to lou_translate
Remove the second indocumented argument to lou_translate

lou_translate has had an undocumented feature to directly specify a
file to translate instead of piping it in via stdin. The feature was
added by Mike Gray in commit f0dd65e7a4. This code crashes if a
non-existing file is passed in (see #849).

This PR takes a different approach at preventing this crash than the
previous PR (#850).

In the spirit of "less is more", instead of making the code more
tamper proof and documenting it, we simply remove this feature.

The behaviour can easily be had by using `lou_translate foo.tbl < bar.txt`

Fixes #849

Supercedes #850

liblouis/liblouis,hammera/liblouis,BueVest/liblouis,BueVest/liblouis,liblouis/liblouis,BueVest/liblouis,hammera/liblouis,BueVest/liblouis,hammera/liblouis,liblouis/liblouis,liblouis/liblouis,liblouis/liblouis,liblouis/liblouis,hammera/liblouis,hammera/liblouis,BueVest/liblouis,BueVest/liblouis,hammera/liblouis