PR tree-optimization/83671 - Fix for false positive reported by -Wstringop-overflow does not work with inlining

gcc/testsuite/ChangeLog:

	PR tree-optimization/83671
	* gcc.dg/strlenopt-40.c: New test.
	* gcc.dg/strlenopt-41.c: New test.

gcc/ChangeLog:

	PR tree-optimization/83671
	* builtins.c (c_strlen): Unconditionally return zero for the empty
	string.
	Use -Warray-bounds for warnings.
	* gimple-fold.c (get_range_strlen): Handle non-constant lengths
	for non-constant array indices with COMPONENT_REF, arrays of
	arrays, and pointers to arrays.
	(gimple_fold_builtin_strlen): Determine and set length range for
	non-constant character arrays.

From-SVN: r256457