builtins.c (expand_builtin_mathfn_2): Use tree_cons to build up the stabilized argume...

builtins.c (expand_builtin_mathfn_2): Use tree_cons to build up the stabilized argument list, not build_tree_list.

	* builtins.c (expand_builtin_mathfn_2): Use tree_cons to build
	up the stabilized argument list, not build_tree_list.
	(expand_builtin_strcpy): Construct new argument list manually
	instead of using chainon to modify the original argument list.
	(expand_builtin_stpcpy): Construct new argument list manually
	instead of using copy_list and chainon.
	(expand_builtin_sprintf): New function.  Optimize calls to
	sprintf when the format is "%s" or doesn't contain a '%'.
	(expand_builtin): Expand BUILT_IN_SPRINTF using the new function
	expand_builtin_sprintf.

	* gcc.c-torture/execute/string-opt-16.c: New test case.

From-SVN: r68355