(divorced petitioner not entitled to either dependency exemption deduction or child tax credit for daughter; decree allowed petitioner to claim dependency exemption and child tax credit in even-numbered years if current on child support obligation; petitioner did not attach Form 8332 or similar document to return, but only attached copy of decree; child not petitioner's qualifying child under I.R.C. Sec. 152(c) and is, therefore, not entitled to child tax credit).