v1: A first attempt at a Pair class.  For now, the fields are public,
there's one constructor and two getters, and everything else is default.

v2: We've added an explicit copy-constructor, an explicit assignment operator, and an explicit destructor; all three of them, as well as the regular constructor, print a message saying what they're doing.  The regular constructor has been modified to default its arguments to 0,
which makes
	const Pair origin;
legal code in the main program.
To illustrate the creation and destruction of variables in local scope,
I've put several lines of the main program into a nested block; the "result" variable is local to this block, so when we get to the end of this block, the destructor is called on it.

v3: Added an == operator, implemented as a stand-alone function.  This function needs to see the fields of the Pair, so they need to be public (or the operator needs to be a "friend", which we haven't discussed yet).

v4: Re-implemented == as a method of the Pair class.  Since it's in the class, it can now see the fields even if they're private, so I made them private.