analyzer: remove -Wanalyzer-use-of-uninitialized-value for GCC 10

analyzer: remove -Wanalyzer-use-of-uninitialized-value for GCC 10

From what I can tell -Wanalyzer-use-of-uninitialized-value has not
yet found a true diagnostic in real-world code, and seems to be
particularly susceptible to false positives.  These relate to bugs in
the region_model code.

For GCC 10 it seems best to remove this warning, which this patch does.
Internally it also removes POISON_KIND_UNINIT.

I'm working on a rewrite of the region_model code for GCC 11 that I
hope will fix these issues, and allow this warning to be reintroduced.

gcc/analyzer/ChangeLog:
	PR analyzer/94447
	PR analyzer/94639
	PR analyzer/94732
	PR analyzer/94754
	* analyzer.opt (Wanalyzer-use-of-uninitialized-value): Delete.
	* program-state.cc (selftest::test_program_state_dumping): Update
	expected dump result for removal of "uninit".
	* region-model.cc (poison_kind_to_str): Delete POISON_KIND_UNINIT
	case.
	(root_region::ensure_stack_region): Initialize stack with null
	svalue_id rather than with a typeless POISON_KIND_UNINIT value.
	(root_region::ensure_heap_region): Likewise for the heap.
	(region_model::dump_summary_of_rep_path_vars): Remove
	summarization of uninit values.
	(region_model::validate): Remove check that the stack has a
	POISON_KIND_UNINIT value.
	(poisoned_value_diagnostic::emit): Remove POISON_KIND_UNINIT
	case.
	(poisoned_value_diagnostic::describe_final_event): Likewise.
	(selftest::test_dump): Update expected dump result for removal of
	"uninit".
	(selftest::test_svalue_equality): Remove "uninit" and "freed".
	* region-model.h (enum poison_kind): Remove POISON_KIND_UNINIT.

gcc/ChangeLog:
	PR analyzer/94447
	PR analyzer/94639
	PR analyzer/94732
	PR analyzer/94754
	* doc/invoke.texi (Static Analyzer Options): Remove
	-Wanalyzer-use-of-uninitialized-value.
	(-Wno-analyzer-use-of-uninitialized-value): Remove item.

gcc/testsuite/ChangeLog:
	PR analyzer/94447
	PR analyzer/94639
	PR analyzer/94732
	PR analyzer/94754
	* gcc.dg/analyzer/data-model-1.c: Mark "use of uninitialized
	value" warnings as xfail for now.
	* gcc.dg/analyzer/data-model-5b.c: Remove uninitialized warning.
	* gcc.dg/analyzer/pr94099.c: Mark "uninitialized" warning as xfail
	for now.
	* gcc.dg/analyzer/pr94447.c: New test.
	* gcc.dg/analyzer/pr94639.c: New test.
	* gcc.dg/analyzer/pr94732.c: New test.
	* gcc.dg/analyzer/pr94754.c: New test.
	* gcc.dg/analyzer/zlib-6.c: Mark "uninitialized" warning as xfail
	for now.