select: switch to macros in uppercase

Curl_select_ready() was the former API that was replaced with
Curl_select_check() a while back and the former arg setup was provided
with a define (in order to leave existing code unmodified).

Now we instead offer SOCKET_READABLE and SOCKET_WRITABLE for the most
common shortcuts where only one socket is checked. They're also more
visibly macros.

lib/ssh.c

@@ -2860,7 +2860,7 @@ static CURLcode ssh_block_statemach(struct connectdata *conn,
       if(LIBSSH2_SESSION_BLOCK_OUTBOUND & dir)
         fd_write = sock;
       /* wait for the socket to become ready */
-      Curl_socket_ready(fd_read, fd_write,
+      Curl_socket_check(fd_read, CURL_SOCKET_BAD, fd_write,
                         left>1000?1000:left); /* ignore result */
     }
 #endif