use [] instead of {} in tests for empty seq
new type abbreviation {} for empty iterable
change type of expression {} to type {}
spec new {} type abbreviation
Added DeclarationCompleter to compute actual/refinedDeclaration lazily for ceylon/ceylon-compiler#1631
ExpressionVisitor: add actual/shared annotations to the model of shortcut refined members

This way they are in line with manual declarations
Util: remove Array from overloading computations, as interop does not use c.l.Array for variadic methods
ModuleValidator: don't traverse the language module dependencies unless we're compiling it ceylon/ceylon-compiler#1631
fix #978
Setting proper file encoding during compilation (ceylon/ceylon-dist#42)
.. and : now apply only to Enumerables
sealed classes/interfaces
Create MissingToken type to avoid calling Token.getText for nothing

because it's expensive for non-missing tokens
Replaces two foreach with c-for to cut down on memory allocation
Optim: rather ugly c-fors are cheaper than foreach
Optim: use this if simplify won't do anything
Optim: TypeDeclaration: Sets are cheaper than List
cosmetic: whitespace
prohibit instantiation of sealed classes
spec for #623
update spec for #451