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 g;

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

void func(char[] str)
{
    printf("%.*s\n", str.length, str.ptr);
}

void main()
{
    char[] arr = "Hello World!";
    func(arr);
    func("ditto");
}