The problem

lately, several ancient language tables have been added to liblouis. In these tables, it is usually desirable to combine several languages/scripts in one table (e.g. English and Greek). However, the greek letter alpha (α) has the same braille pattern as the latin letter a, and there are many more such cases.

Proposed solution

In liblouis, in a single table we'd be able to define characters with an additional class (e.g. the foreign class in nl-NL-g0.utb). Then, we use modeletter, begmodeword, etc. to ensure that foreign characters, words or phrases have a braille indicator.
I propose the ability that we extend the include opcode with the ability to map every character definition to an additional character class.
E.g.

include grc-international-composed.uti greek
modeletter greek 2356
...

This should:

1. include grc-international-composed.uti
2. For every character opcode in the include file, add an additional definition for the greek attribute class

Now, every Greek letter in the resulting table will be prepended by braille pattern 2356, making it possible to distinguish the alpha from the a, the beta from the b, etc.