Partial reimplementation of compiler and TypeTable

Every type symbol and its possible polymorphic variables are now
parsed up front and put in the SymbolTable, doing away with the
complicated and error-prone NamespacedIdentifier. Still pending
changes to parts of the compiler and the runtime, so not working
at the moment.

Preparatory work for union literals

Contains horrible parsing hacks that transmute function calls and
enum literals to union literals if appropriate. Pending the
implementation of the tokenizer the AST can be constructed more
neatly.