Constify some arguments in Curl_connecthost() and singleipconnect().

lib/connect.c

@@ -109,7 +109,7 @@ static bool verifyconnect(curl_socket_t sockfd, int *error);
 
 static curl_socket_t
 singleipconnect(struct connectdata *conn,
-                Curl_addrinfo *ai, /* start connecting to this */
+                const Curl_addrinfo *ai, /* start connecting to this */
                 long timeout_ms,
                 bool *connected);
 
@@ -676,7 +676,7 @@ static void nosigpipe(struct connectdata *conn,
    having connected if used from the multi interface. */
 static curl_socket_t
 singleipconnect(struct connectdata *conn,
-                Curl_addrinfo *ai,
+                const Curl_addrinfo *ai,
                 long timeout_ms,
                 bool *connected)
 {
@@ -778,7 +778,7 @@ singleipconnect(struct connectdata *conn,
  */
 
 CURLcode Curl_connecthost(struct connectdata *conn,  /* context */
-                          struct Curl_dns_entry *remotehost, /* use this one */
+                          const struct Curl_dns_entry *remotehost, /* use this one */
                           curl_socket_t *sockconn,   /* the connected socket */
                           Curl_addrinfo **addr,      /* the one we used */
                           bool *connected)           /* really connected? */

lib/connect.h

@@ -31,7 +31,7 @@ CURLcode Curl_is_connected(struct connectdata *conn,
                            bool *connected);
 
 CURLcode Curl_connecthost(struct connectdata *conn,
-                          struct Curl_dns_entry *host, /* connect to this */
+                          const struct Curl_dns_entry *host, /* connect to this */
                           curl_socket_t *sockconn, /* not set if error */
                           Curl_addrinfo **addr, /* the one we used */
                           bool *connected /* truly connected? */