Function libxslt::bindings::xmlXPathRegisterFuncNS

pub unsafe extern "C" fn xmlXPathRegisterFuncNS(
    ctxt: *mut _xmlXPathContext, 
    name: *const u8, 
    ns_uri: *const u8, 
    f: Option<unsafe extern "C" fn(*mut _xmlXPathParserContext, i32)>
) -> i32