Text is preprocessed and made into words and sentences. In order to do the latter we need to handle abbreviations. The linguistic sides of the issue are found in this document, here we look at the compilation.
In order to compile the file abbr.txt (which you will need to find the correct sentence border), do the following:
(we assume you stand in the catalogue of your language)
cd tools/preprocess make abbr
The best solution would be to have this compilation as part of the ordinary make process, this is still not in place.