Define an AST with no currying semantics and translate to it

[vaivaswatha]

PR #23 did a poor attempt at doing the same thing, without redefining Scilla's typ to accommodate functions with multiple arguments. This PR does it all neatly.

This PR defines an AST with the following differences with Scilla's AST:

FunType of typ * typ is now defined as FunType of (typ list) * typ and the expression Fun of ident * typ * expr is defined as Fun (ident * typ) list * expr . The definition of App remains same, except that its semantics is no more that of currying. So the translation pass splits existing App into a sequence of Apps. For example y = f a b (in the original Scilla semantics) now becomes x = f a; y = x b

In the future, we can easily do a decurrying optimization on this new AST to optimize function calls (see #24) .

[vaivaswatha]

@jjcnn , the code change is quite huge, but most of it is mundane adaptations of functions from TypeUtilities and Datatypes.

The key items to review are: (1) typ and expr definition in UncurriedSyntax.ml and the translation of Fun and App in Uncurry.ml.

[vaivaswatha]

Thank you @jjcnn