add operand alias to operators

[mei-ye]

need to find a way to annotate operand-alias in operators/operations/instructions so that program analysis does not need to add specialized checks for each operators.

[pfultz2]

The operator need an optional method to get which argument it aliases on output, and return a negative number if it doesn't alias any input argument. Until then, we can write a function to use a basic heuristic:

int get_alias_output(instruction_ref x)
{
    // Nothing to alias
    if(x->arguments.empty())
        return -1;
    // Assume functions that use an allocation as the last parameter is aliased
    if(x->arguments.back()->op.name() == "hip::allocate")
        return x->arguments.size() - 1;
    return -1;
}

Then replace the function with a call to the operation class when it gets implemented.

[pfultz2]

This is actually a duplicate of #23.