Flc() generates more files than flex does. While flex only generates a
tt(lex.yy.cc), flc() generates several header files and a source file: by
default tt(Scanner.h), tt(Scanner.ih), tt(Scannerbase.h), and tt(lex.cc). Both
tt(Scannerbase.h) and tt(lex.cc) are overwritten when flc() is invoked.

tt(Scanner.h) and tt(Scanner.ih) are only generated the first time flc() is
called. These files can thereafter be modified by the user (e.g., to add
members to the tt(Scanner) class). 

