analyzer: new warning: -Wanalyzer-undefined-behavior-strtok [PR107573]

analyzer: new warning: -Wanalyzer-undefined-behavior-strtok [PR107573]

This patch:
- adds support to the analyzer for tracking API-private state
  or which we don't have a decl (such as strtok's internal state),
- uses it to implement a new -Wanalyzer-undefined-behavior-strtok which
  warns when strtok (NULL, delim) is called as the first call to
  strtok after main.

gcc/analyzer/ChangeLog:
	PR analyzer/107573
	* analyzer.h (register_known_functions): Add region_model_manager
	param.
	* analyzer.opt (Wanalyzer-undefined-behavior-strtok): New.
	* call-summary.cc
	(call_summary_replay::convert_region_from_summary_1): Handle
	RK_PRIVATE.
	* engine.cc (impl_run_checkers): Pass model manager to
	register_known_functions.
	* kf.cc (class undefined_function_behavior): New.
	(class kf_strtok): New.
	(register_known_functions): Add region_model_manager param.
	Use it to register "strtok".
	* region-model-manager.cc
	(region_model_manager::get_or_create_conjured_svalue): Add "idx"
	param.
	* region-model-manager.h
	(region_model_manager::get_or_create_conjured_svalue): Add "idx"
	param.
	(region_model_manager::get_root_region): New accessor.
	* region-model.cc (region_model::scan_for_null_terminator): Handle
	"expr" being null.
	(region_model::get_representative_path_var_1): Handle RK_PRIVATE.
	* region-model.h (region_model::called_from_main_p): Make public.
	* region.cc (region::get_memory_space): Handle RK_PRIVATE.
	(region::can_have_initial_svalue_p): Handle MEMSPACE_PRIVATE.
	(private_region::dump_to_pp): New.
	* region.h (MEMSPACE_PRIVATE): New.
	(RK_PRIVATE): New.
	(class private_region): New.
	(is_a_helper <const private_region *>::test): New.
	* store.cc (store::replay_call_summary_cluster): Handle
	RK_PRIVATE.
	* svalue.h (struct conjured_svalue::key_t): Add "idx" param to
	ctor and "m_idx" field.
	(class conjured_svalue::conjured_svalue): Likewise.

gcc/ChangeLog:
	PR analyzer/107573
	* doc/invoke.texi: Add -Wanalyzer-undefined-behavior-strtok.

gcc/testsuite/ChangeLog:
	PR analyzer/107573
	* c-c++-common/analyzer/strtok-1.c: New test.
	* c-c++-common/analyzer/strtok-2.c: New test.
	* c-c++-common/analyzer/strtok-3.c: New test.
	* c-c++-common/analyzer/strtok-4.c: New test.
	* c-c++-common/analyzer/strtok-cppreference.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>