A simple class for testing membership of a fixed set of case-insensitive ASCII strings.
The class must be initialised with enough space for all the strings,
it will go into an infinite loop if it fills. The string matching is case-blind,
using an algorithm that works only for ASCII.
The class implements part of the java.util.Set interface; it could be replaced with
an implementation of java.util.Set together with a class that implemented a customized