The State class contains the data describing various states.
Each State has a type, defined in the Type enum, and depending on the state
type different data are required. 

State objects contain a Type and StateData *. Sometimes the StateData * can be
0, (e.g., with type FINAL), usually it contains two size_t fields holding
indices in vector<State> d_state where the next state is found on a
transition, sometimes the transition is a concatenation of characters stored
in a std::string, and StateData * points to a struct containing the indices
and a std::string. 

StateData, therefore is polymorphic. 

To facilitate assignment to d_state State defines several static 
`factory members' (called `factory' in various overloaded forms) 
producing the required State object.

State is a traditional class offering pointers. It has a copy constructor,
overloaded assignment operator and swap-functionality.


The special character EOF__
===========================

TODO: BOL handling has been changed, and there's no special BOL character
anymore. This section of the README file needs an update -- FBB 7/5/2011


The special characters BOL and EOF__ are transformed by Ranges to d_nsubsets +
1 and d_nsubsets + 2 and are entering the DFA as normal characters.

However, when lex() executes it will inspect the DFA for a BOL transition when
called following the processing of a \n character. If the DFA contains a BOL
it handles that transition and only then it will process the next character
from its input buffer. If the DFA does not contain a BOL transition the next
character is directly processed.

If an EOF is returned and the DFA contains an EOF transition it will perform
that transition. If not and there are files on the FileInfo stack the next
file is popped and processing continues with the next available character. If
neither takes place lex returns -1.
