In my April 2 column, I laid out some of the rules for getting credit for active-duty military service time in your federal civilian annuity. This time, I’ll explain how you can make a deposit to the Civil Service Retirement Fund — if you decide it’s to your advantage to claim any credit you are due. For most of you, the decision about making or not making a deposit to gain military service credit in your annuity will be a matter of dollars and cents. You’ll have to compare the amount you owe to the retirement fund against what you would…