Function cups_sys::ippAddStringfv

pub unsafe extern "C" fn ippAddStringfv(
    ipp: *mut ipp_t, 
    group: ipp_tag_t, 
    value_tag: ipp_tag_t, 
    name: *const c_char, 
    language: *const c_char, 
    format: *const c_char, 
    ap: *mut __va_list_tag
) -> *mut ipp_attribute_t