... if there are more than one using the same name
Returns the value for the given header name (or NULL). This is a shortcut so
that the application doesn't have to loop through all headers to find the one
it is interested in. The data pointed will be freed when this callback
-returns.
+returns. If more than one header field use the same name, this returns only
+the first one.
.SH CALLBACK RETURN VALUE
.IP "CURL_PUSH_OK (0)"
The application has accepted the stream and it can now start receiving data,