**_Born under a bad sign_** In a Southern Cal town people are dying in curious circumstances with everything pointing to some unlikely culprits. “Bloody Birthday” (1981) mixes the killer kid genre with slasher flick and works well enough. It came out a few years before the “Children of the Corn” series started, but it’s not like there weren’t plenty of predecessors going back to the early 60s. For instance, the Star Trek TV series had two episodes with sinister children, “Miri” and “The Children Shall Lead.” Then there’s “The Brood,” which debuted a couple years earlier. Elizabeth H...