Convert AS Number to standardized asplain notation as an integer.

def as_number(as_number_val):
    """Convert AS Number to standardized asplain notation as an integer."""
    as_number_str = py23_compat.text_type(as_number_val)
    if "." in as_number_str:
        big, little = as_number_str.split(".")
        return (int(big) << 16) + int(little)
    else:
        return int(as_number_str)