Delmar Hall, the new 800-capacity concert venue currently under construction in the Delmar Loop, will officially open its doors on September 30 with a show by reunited St. Louis rockers Stir.The venue made the announcement today via its Facebook page. The two weeks to follow the grand opening will also see stops by Jay Farrar on October 1 (playing Son Volt's Trace) and California punk band Pennywise on October 7 (along with Strung Out and Unwritten Law).…