analyzer: use objects for state_machine::state_t

analyzer: use objects for state_machine::state_t

This patch is preliminary work towards generalizing sm-malloc.cc so that
it can check APIs other than just malloc/free (and e.g. detect
mismatching alloc/dealloc pairs).

Generalize states in state machines so that, rather than state_t being
just an "unsigned", it becomes a "const state *", where the underlying
state objects are immutable objects managed by the state machine in
question, and can e.g. have vfuncs and extra fields.  The start state
m_start becomes a member of the state_machine base_class.

gcc/analyzer/ChangeLog:
	* checker-path.cc (state_change_event::get_desc): Update
	state_machine::get_state_name calls to state::get_name.
	(warning_event::get_desc): Likewise.
	* diagnostic-manager.cc
	(null_assignment_sm_context::on_transition): Update comparison
	against 0 with comparison with m_sm.get_start_state.
	(diagnostic_manager::prune_for_sm_diagnostic): Update
	state_machine::get_state_name calls to state::get_name.
	* engine.cc (impl_sm_context::on_transition): Likewise.
	(exploded_node::get_dot_fillcolor): Use get_id when summing
	the sm states.
	* program-state.cc (sm_state_map::sm_state_map): Don't hardcode
	0 as the start state when initializing m_global_state.
	(sm_state_map::print): Use dump_to_pp rather than get_state_name
	when dumping states.
	(sm_state_map::is_empty_p): Don't hardcode 0 as the start state
	when examining m_global_state.
	(sm_state_map::hash): Use get_id when hashing states.
	(selftest::test_sm_state_map): Use state objects rather than
	arbitrary hardcoded integers.
	(selftest::test_program_state_merging): Likewise.
	(selftest::test_program_state_merging_2): Likewise.
	* sm-file.cc (fileptr_state_machine::m_start): Move to base class.
	(file_diagnostic::describe_state_change): Use get_start_state.
	(fileptr_state_machine::fileptr_state_machine): Drop m_start
	initialization.
	* sm-malloc.cc (malloc_state_machine::m_start): Move to base
	class.
	(malloc_diagnostic::describe_state_change): Use get_start_state.
	(possible_null::describe_state_change): Likewise.
	(malloc_state_machine::malloc_state_machine): Drop m_start
	initialization.
	* sm-pattern-test.cc (pattern_test_state_machine::m_start): Move
	to base class.
	(pattern_test_state_machine::pattern_test_state_machine): Drop
	m_start initialization.
	* sm-sensitive.cc (sensitive_state_machine::m_start): Move to base
	class.
	(sensitive_state_machine::sensitive_state_machine): Drop m_start
	initialization.
	* sm-signal.cc (signal_state_machine::m_start): Move to base
	class.
	(signal_state_machine::signal_state_machine): Drop m_start
	initialization.
	* sm-taint.cc (taint_state_machine::m_start): Move to base class.
	(taint_state_machine::taint_state_machine): Drop m_start
	initialization.
	* sm.cc (state_machine::state::dump_to_pp): New.
	(state_machine::state_machine): Move here from sm.h.  Initialize
	m_next_state_id and m_start.
	(state_machine::add_state): Reimplement in terms of state objects.
	(state_machine::get_state_name): Delete.
	(state_machine::get_state_by_name): Reimplement in terms of state
	objects.  Make const.
	(state_machine::validate): Delete.
	(state_machine::dump_to_pp): Reimplement in terms of state
	objects.
	* sm.h (state_machine::state): New class.
	(state_machine::state_t): Convert typedef from "unsigned" to
	"const state_machine::state *".
	(state_machine::state_machine): Move to sm.cc.
	(state_machine::get_default_state): Use m_start rather than
	hardcoding 0.
	(state_machine::get_state_name): Delete.
	(state_machine::get_state_by_name): Make const.
	(state_machine::get_start_state): New accessor.
	(state_machine::alloc_state_id): New.
	(state_machine::m_state_names): Drop in favor of...
	(state_machine::m_states): New field
	(state_machine::m_start): New field
	(start_start_p): Delete.