Fix incorrect tuple type in case of low level call

[montyly]

The incorrect tuple types were only present for low level calls with solidity >= 0.5 (low level call return a tuple instead of a bool from 0.5)

Fix #529
Replace #536

Tested with

library Lib{

    function t() public returns(uint, bool){

    }
}

contract Tuple {

  function f()
    public
  {
    bool success;
    address dest;
    bytes memory returnValue;
    (success, returnValue) = dest.call("");
  }

  function get() internal returns(uint, bool);

  function test() public{
        uint a;
        bool b;
        (a,b) = get();

        (a,b) = Lib.t();
  }

}

Contract Tuple	Function Tuple.f() (*)
		Expression: (success,returnValue) = dest.call()
		IRs:
			TUPLE_0(bool,bytes) = LOW_LEVEL_CALL, dest:dest, function:call, arguments:['']  
			success(bool)= UNPACK TUPLE_0 index: 0 
			returnValue(bytes)= UNPACK TUPLE_0 index: 1 
	Function Tuple.get() (*)
	Function Tuple.test() (*)
		Expression: (a,b) = get()
		IRs:
			TUPLE_1(uint256,bool) = INTERNAL_CALL, Tuple.get()()
			a(uint256)= UNPACK TUPLE_1 index: 0 
			b(bool)= UNPACK TUPLE_1 index: 1 
		Expression: (a,b) = Lib.t()
		IRs:
			TUPLE_2(uint256,bool) = LIBRARY_CALL, dest:Lib, function:t, arguments:[] 
			a(uint256)= UNPACK TUPLE_2 index: 0 
			b(bool)= UNPACK TUPLE_2 index: 1