analyzer: cleanups to checker_path

analyzer: cleanups to checker_path

This patch adds DISABLE_COPY_AND_ASSIGN to checker_path, and makes its
fields private.

gcc/analyzer/ChangeLog:
	* checker-path.h (checker_path::get_checker_event): New function.
	(checker_path): Add DISABLE_COPY_AND_ASSIGN; make fields private.
	* diagnostic-manager.cc
	(diagnostic_manager::prune_for_sm_diagnostic): Replace direct
	access to checker_path::m_events with accessor functions.  Fix
	overlong line.
	(diagnostic_manager::prune_interproc_events): Replace direct
	access to checker_path::m_events with accessor functions.
	(diagnostic_manager::finish_pruning): Likewise.