Deprecate ADD_AREA_REGION_TRIGGER

[FredrikLindgren]

The parameter names for the function differ from the parameter names of the macro; the documentation is correct, but fun_args complains and the function defaults do nothing. The functionality is wholly eclipsed by fj_are_structure; use that instead. Probably fix up the names of the function parameters to match the documentation, so legacy code won't trigger fun_args warnings.