clarify that when curl_multi_timeout() returns -1 it just means that there

is no current timeout. It does not mean wait forever and it does not mean
do not wait at all. It means there is no timeout value known at this point in
time.

docs/libcurl/curl_multi_timeout.3

@@ -23,6 +23,10 @@ The timeout value returned in the long \fBtimeout\fP points to, is in number
 of milliseconds at this very moment. If 0, it means you should proceed
 immediately without waiting for anything. If it returns -1, there's no timeout
 at all set.
+
+Note: if libcurl returns a -1 timeout here, it just means that libcurl
+currently has no stored timeout value. You must not wait too long (more than a
+few seconds perhaps) before you call curl_multi_perform() again.
 .SH "RETURN VALUE"
 The standard CURLMcode for multi interface error codes.
 .SH "TYPICAL USAGE"