re PR tree-optimization/79800 (wrong snprintf result range with precision in a narrow negative-positive range)

	PR tree-optimization/79800
	* gimple-ssa-sprintf.c (format_floating: Add argument.  Handle
	precision in negative-positive range.
	(format_floating): Call non-const overload with adjusted precision.

	PR tree-optimization/79800
	* gcc.dg/tree-ssa/builtin-sprintf-warn-15.c: Add test cases.
	* gcc.dg/tree-ssa/pr79800.c: New test.

From-SVN: r246151