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 bug21;
extern(C) int printf(char*, ...);

void main()
{
    int i = 42;
    auto a = {
        int j = i*2;
        auto b = {
            return j;
        };
        return b();
    };
    int i2 = a();
    printf("%d\n", i2);
    assert(i2 == i*2);
}