Shrinking drill hole size in Eagle
There is an User Language Program (ULP) for this, in the standard distribution. It is called drill-aid.ulp.

You run it on your finished PCB, before printing. it will make all the drilled pads smaller, making it easier to drill manually. As a side effect, you will get the requested function.

It will generate the extra copper in a separate layer, so that it can be removed and re-generated if you modify the board.