[OPTIM] move some rarely used fields out of fdtab

Some rarely information are stored in fdtab, making it larger for no
reason (source port ranges, remote address, ...). Such information
lie there because the checks can't find them anywhere else. The goal
will be to move these information to the stream interface once the
checks make use of it.

For now, we move them to an fdinfo array. This simple change might
have improved the cache hit ratio a little bit because a 0.5% of
performance increase has measured.
diff --git a/src/checks.c b/src/checks.c
index 0e9aca5..e7aefb4 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -838,19 +838,19 @@
 							/* note: in case of retry, we may have to release a previously
 							 * allocated port, hence this loop's construct.
 							 */
-							port_range_release_port(fdtab[fd].port_range, fdtab[fd].local_port);
-							fdtab[fd].port_range = NULL;
+							port_range_release_port(fdinfo[fd].port_range, fdinfo[fd].local_port);
+							fdinfo[fd].port_range = NULL;
 
 							if (!bind_attempts)
 								break;
 							bind_attempts--;
 
-							fdtab[fd].local_port = port_range_alloc_port(s->sport_range);
-							if (!fdtab[fd].local_port)
+							fdinfo[fd].local_port = port_range_alloc_port(s->sport_range);
+							if (!fdinfo[fd].local_port)
 								break;
 
-							fdtab[fd].port_range = s->sport_range;
-							src.sin_port = htons(fdtab[fd].local_port);
+							fdinfo[fd].port_range = s->sport_range;
+							src.sin_port = htons(fdinfo[fd].local_port);
 
 							ret = tcpv4_bind_socket(fd, flags, &src, remote);
 						} while (ret != 0); /* binding NOK */
@@ -926,8 +926,8 @@
 						fdtab[fd].cb[DIR_RD].b = NULL;
 						fdtab[fd].cb[DIR_WR].f = &event_srv_chk_w;
 						fdtab[fd].cb[DIR_WR].b = NULL;
-						fdtab[fd].peeraddr = (struct sockaddr *)&sa;
-						fdtab[fd].peerlen = sizeof(sa);
+						fdinfo[fd].peeraddr = (struct sockaddr *)&sa;
+						fdinfo[fd].peerlen = sizeof(sa);
 						fdtab[fd].state = FD_STCONN; /* connection in progress */
 						fdtab[fd].flags = FD_FL_TCP | FD_FL_TCP_NODELAY;
 						EV_FD_SET(fd, DIR_WR);  /* for connect status */
@@ -963,8 +963,8 @@
 					}
 				}
 			}
-			port_range_release_port(fdtab[fd].port_range, fdtab[fd].local_port);
-			fdtab[fd].port_range = NULL;
+			port_range_release_port(fdinfo[fd].port_range, fdinfo[fd].local_port);
+			fdinfo[fd].port_range = NULL;
 			close(fd); /* socket creation error */
 		}