Support empty block statements.
Support unary minus operator.
Unify bit and int as int.
Support parsing of pragma declarations.

Currently they are ignored.
Better (static) support for implicit casting.

So we can treat 0 and 1 as bit, and they will be casted to int automatically
(which removes a type ambiguity in miniTest91.sk).

Still needs support in the evaluator (which is why miniTest21.sk broke)
Perform static inlining of global variables.
Statically evaluate integer ops if both arguments are known.
Cleaned up implicit cast.

Also add support for cast from bits to other kinds of arrays.
Fixed precedence of '?:' operator.