fix event-queue and unwind-protect exception warnings * event-queue.h (event_queue_safe::warn_unhandled_exception): New function. (event_queue_safe::gripe_exception): Delete decl. * event-queue.cc: New file. (event_queue_safe::warn_unhandled_exception): New function. * libinterp/corefcn/module.mk (COREFCN_SRC): Add it to the list * unwind-prot.cc, unwind-prot.h (unwind_protect_safe::warn_unhandled_exception): Rename from unwind_protect_safe::warn_unhandled_exception. No longer static.

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