WordPerfect and other filters, wrappers for a set of similar libraries

This collection of filters is here in this folder in addition to the
WordPerfect filter that gave the module its (humorous) name "writerperfect"
because the libraries they use all have the same "style" of API and are
developed, at least partially, by the same person or group of persons.

This module uses astyle to keep consistent coding style. Please run

astyle --options=astyle.options \*.?xx

before committing.