Fix in the translation of Rascal type variables.
Working on overloading: extended muRascal grammar and AST; made a
distinction between the use and call of muRascal and Rascal functions.
A few changes to the use of the overloading related info produced by
the type checker; introduced an overloading resolver and overloaded
function store.
Changed the translation of Rascal functions, closures and call
expressions regarding the overloading semantics.
Fix in the Library.mu related to the typed variable match.
Extended RVM instructions with overloading related instructions;
implemented these new instructions (certain improvements still need to
be made).
Merged.