Fix some unittests for 64-bit asm. They were operating on int variables as if they were longs. This was causing asm1_1 to fail when compiled with -O3 because it was overwriting the spilled value of callee-saved register %rbx, which the runtime was using as a pointer value at the time.

module mini.norun_debug12;

interface I
{
    int foo();
}

class C : I
{
    int i = 24;
    int foo()
    {
        return i;
    }
}

void main()
{
    scope c = new C;
    I i = c;

    int* fail;
    *fail = 0;
}