analyzer: check format strings for null termination [PR105899]

This patch extends -fanalyzer to check the format strings of calls
to functions marked with '__attribute__ ((format...))'.

The only checking done in this patch is to check that the format string
is a valid null-terminated string; this patch doesn't attempt to check
the content of the format string.

gcc/analyzer/ChangeLog:
	PR analyzer/105899
	* call-details.cc (call_details::call_details): New ctor.
	* call-details.h (call_details::call_details): New ctor decl.
	(struct call_arg_details): Move here from region-model.cc.
	* region-model.cc (region_model::check_call_format_attr): New.
	(region_model::check_call_args): Call it.
	(struct call_arg_details): Move it to call-details.h.
	* region-model.h (region_model::check_call_format_attr): New decl.

gcc/testsuite/ChangeLog:
	PR analyzer/105899
	* gcc.dg/analyzer/attr-format-1.c: New test.
	* gcc.dg/analyzer/sprintf-1.c: Update expected results for
	now-passing tests.

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