clarify what a modern version of libcurl means

docs/libcurl/curl_multi_socket_action.3

@@ -95,13 +95,13 @@ for more actions on libcurl's sockets. You don't have to do it immediately,
 but the return code means that libcurl may have more data available to return
 or that there may be more data to send off before it is "satisfied".
 
-In modern libcurls, \fICURLM_CALL_MULTI_PERFORM\fP or
-\fICURLM_CALL_MULTI_SOKCET\fP should not be returned and no application needs
-to care about them.
+In modern libcurls (from around 7.19.0 or later),
+\fICURLM_CALL_MULTI_PERFORM\fP or \fICURLM_CALL_MULTI_SOKCET\fP will not be
+returned and no application needs to care about them.
 
-NOTE that the return code is for the whole multi stack. Problems still might have
-occurred on individual transfers even when one of these functions
-return OK.
+NOTE that the return code from this function is for the whole multi stack.
+Problems still might have occurred on individual transfers even when one of
+these functions return OK.
 .SH "TYPICAL USAGE"
 1. Create a multi handle