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.assign1;

extern(C) int printf(char*, ...);

struct X
{
    int a;
    alias a b;
}
void main()
{
    X e = void;
    e.a = e.b = 5;
    printf("%d - %d\n", e.a, e.b);
    assert(e.a == 5);
    assert(e.a == e.b);
}