use build_function_type less in c-family and LTO
gcc/c-family/
	* c-common.c (def_fn_type): Don't call build_function_type, call
	build_function_type_array or build_varargs_function_type_array
	instead.
	(c_common_nodes_and_builtins): Likewise.

gcc/lto/
	* lto-lang.c (def_fn_type): Don't call build_function_type, call
	build_function_type_array or build_varargs_function_type_array
	instead.

From-SVN: r173623