Updated Hungarian translation
Release 3.7.1
Doc: fix header to include for the word completion provider
CompletionModel: better format the prototypes
CompletionModel: simplify the creation of the signals

The function pointers in GtkSourceCompletionModelClass are useless
because there is no subclass of CompletionModel (which is a private
class).
CompletionModel: rename three functions

I remember that when reading the code the first time it was difficult to
understand the purpose of those functions. Since the API is private,
there is no renaming problems.