Compiler: implement the tuple syntax

Created by: vaussard

The tuple (delimited by parentheses) appears to be a nice tool to solve a number of issues, for example issue #44 (closed), #45 (closed) and #77 (closed).

A number of examples:

var foo = (1, 2, 3) emit bar (5, 2, 6) call math.copy(toto, (x+3*(1/2), y, z))