"For purposes of this chapter, the term “employee” includes an officer, employee, or elected official of the United States, a State, or any political subdivision thereof, or the District of Columbia, or any agency or instrumentality of any one or more of the foregoing. The term “employee” also includes an officer of a corporation." This definition does not exclude all those who are commonly known as 'employees'. “Similarly, Latham’s instruction which indicated that under 26 U.S.C. § 3401(c) the category of ‘employee’ does not include privately employed wage earners is a preposterous reading of the statute. It is obvious that within the context of both statutes the word ‘includes’ is a term of enlargement not of limitation, and the reference to certain entities or categories is not intended to exclude all others.”