Call checking

[mrRachar]

Currently no attempt is made to check the arity or types of parameters for calls. The following compiles:

contract Test { }

Test :: (any) {
    public init() {
        // None of the following should work, but all do
        test0(true)

        test1()
        test1(1)
        test1(true, 1)

        test2()
        test2(1)
        test2(true)
        test2(true, 3)
        test2(1, 2, 3)
    }

    func test0() -> Int {
        return 0
    }

    func test1(x: Bool) -> Int {
        return 1
    }

    func test2(x: Int, y: Int) -> Int {
        return 2
    }
}

It will, however, produce invalid target code. This issue is similar to #15 ''(Type checking)'' although also has issues with call arity, and the lack of proper call-site function inspection is also a problem for #6.