Identifiers can start with '_'.
Add support for == and /= on general arrays.
Added internal support for multi-variable declarations.

The parser does not yet support them.
Added parser support for multi variable declarations.
Added internal support for post increment operator.
Added internal support for the rest of the increment operators.
Support incr operators in expressions.

Currently they only support pre/post incr/decr  of identifiers.
Support arbitrary ExprS for for increment.
Make Value an instance of Ord.

Makes things slightly cleaner I think.
Made Value an instance of Num.

Things are maybe a little cleaner now.
Some fun with liftM2 and <$> to shorten code.
Added += expression.
Allow expr in general for a statement.

Instead of special casing the increment operators.
Support increment operators on lvals in general, not just id.