Suggestion: typechecking for asm.js

[RyanCavanaugh]

Support detecting "use asm" directives and change type inference and operator rules accordingly

"use asm";
var x = 0; // x: int
var y = 0.0: // y: float
var z = (x + y) | 0; // z: int
z = 0.4; // Error, cannot convert float to int

We would need a complete set of type rules for this.

[RyanCavanaugh]

asm.js type system is too different from TypeScript's for this to be useful/feasible.