Before there were microwaves, computers and Wal-Marts, Pastor James C. Crist Sr. was serving the Lord.     And Aug. 21, his church — Magnolia Baptist Church, Brewton (Escambia Baptist Association) — honored that legacy by celebrating his 80th birthday and the 57 of those 80 years that have been spent in the ministry.     “It’s a calling,” Crist said. “God…