analyzer: precision-of-wording for -Wanalyzer-stale-setjmp-buffer

analyzer: precision-of-wording for -Wanalyzer-stale-setjmp-buffer

This patch adds a custom event to paths emitted by
-Wanalyzer-stale-setjmp-buffer highlighting the place where the
pertinent stack frame is popped, and updates the final event in
the path to reference this.

gcc/analyzer/ChangeLog:
	* checker-path.h (checker_event::get_id_ptr): New.
	* diagnostic-manager.cc (path_builder::path_builder): Add "sd"
	param and use it to initialize new field "m_sd".
	(path_builder::get_pending_diagnostic): New.
	(path_builder::m_sd): New field.
	(diagnostic_manager::emit_saved_diagnostic): Pass sd to
	path_builder ctor.
	(diagnostic_manager::add_events_for_superedge): Call new
	maybe_add_custom_events_for_superedge vfunc.
	* engine.cc (stale_jmp_buf::stale_jmp_buf): Add "setjmp_point"
	param and use it to initialize new field "m_setjmp_point".
	Initialize new field "m_stack_pop_event".
	(stale_jmp_buf::maybe_add_custom_events_for_superedge): New vfunc
	implementation.
	(stale_jmp_buf::describe_final_event): New vfunc implementation.
	(stale_jmp_buf::m_setjmp_point): New field.
	(stale_jmp_buf::m_stack_pop_event): New field.
	(exploded_node::on_longjmp): Pass setjmp_point to stale_jmp_buf
	ctor.
	* pending-diagnostic.h
	(pending_diagnostic::maybe_add_custom_events_for_superedge): New
	vfunc.

gcc/testsuite/ChangeLog:
	* gcc.dg/analyzer/setjmp-5.c: Update expected path output to show
	an event where the pertinent stack frame is popped.  Update
	expected message from final event to reference this event.