Fix vector example

[DutChen18]

Fixed two issues that are made apparent by the following program:

#include <iostream>

class Obj {};

[[cheerp::genericjs]]
int webMain() {
	std::vector<Obj*> vec;

	vec.push_back(new Obj); // [1]

	std::cout << (int)vec[0] << std::endl;

	if (vec[0] == new Obj) { // [2]
		std::cout << "IDENTICAL" << std::endl;
	} else {
		std::cout << "NOT IDENTICAL" << std::endl;
	}

	return 0;
}

At [1], the call to push_back (a wasm function) should produce a diagnostic because it takes a reference to a pointer.

At [2], the if statement is compiled down to a select instruction, and the strings passed to operator<< are in linear memory. But PA did not follow the operands and would not discover the strings to be in linear memory.