* Support for complex numbers. The standard lexer recoginizes `i` as the imaginary unit.
* ComplexLexer also recognizes `abs` (modulus), `conj` (complex conjugation), `re` (real part) and `im` (imaginary part)
* ComplexEvaluator evaluates all elementary functions with complex arguments. The principal branch is used for `log`, `^`, `sqrt`, and inverse trigonmetric and hyperbolic functions.
* Extensions::Complex contains the actual implementation of complex arithmetic and complex elementary functions
* The standard lexer, parser and evaluator supports `sind`, `cosd` and `tand` for trigonometric functions with arguments in degrees.
* Support for NAN and INF in lexer and parser (implemented as constants)
* Lexer support for floating point numbers on exponential form
* A number of bug fixes in LaTeXPrinter and AscIIPrinter
* Support for factorial (!) and semi-factorial (!!) postfix operators
* Improved exception handling, with easy access to the token, variable, operator etc. that was the cause of the error