PR30879: intermittent debuginfod crash with unhandled exception

PR30879: intermittent debuginfod crash with unhandled exception

Code inspection identified two places where sqlite_ps objects were
being created/used outside try/catch protection.  This patch wraps or
replaces them.

* configure.ac: Look for glibc backtrace headers.
* debuginfod.cxx (scan): New function wrapped by a try/catch loop.
  (sqlite_checkpoint_pb): Use non-exception-producing sqlite functions.
  (main, my_terminate_handler): New terminate() handler.