Add some alignment info where LLVM might otherwise be more pessimistic. In particular, %.nest_arg is always aligned even though it's bitcast from i8*. Pointers in vtables are also guaranteed to be stored at aligned addresses.

module scope1;
extern(C) int printf(char*, ...);
void main()
{
    printf("1\n");
    {
        scope(exit) printf("2\n");
    }
    printf("3\n");
}