cpp/io/basic ostream/vprint unicode

Behaves as (except that some details of error reporting differ):
 * First, the function constructs and checks the object.
 * Then, initializes an automatic variable as if by.
 * Finally, inserts the character sequence into, that is, if  refers to a terminal capable of displaying Unicode, writes  to this terminal using the native Unicode API. Otherwise, writes unmodified  to the.

Return value
(none)