Merge from vendor branch TNF:

Merge from vendor branch TNF:
Initial import of libexttextcat-3.2 from wip, packaged by Francois Tigeot.

Libexttextcat is a library with functions that implement the
classification technique described in Cavnar & Trenkle, "N-Gram-Based
Text Categorization" . It was primarily developed for language
guessing, a task on which it is known to perform with near-perfect
accuracy.