url: bad --connect-to syntax now returns error

[gunhu]

This PR address bad --connect-to syntax.

Before:

$ curl --connect-to ::curl.se:151.101.66.49 https://curl.se -v
* No valid port number in connect to host string (151.101.66.49)
*   Trying 151.101.194.49...
* TCP_NODELAY set
* Connected to curl.se (151.101.194.49) port 443 (#0)

After:

$ ./src/curl --connect-to ::curl.se:curl.se https://curl.se -v
* No valid port number in connect to host string (curl.se)
* Closing connection -1
curl: (49) No valid port number in connect to host string (curl.se)

As always I'm open to any comment.

$ /usr/bin/perl -I. ./runtests.pl 3020
********* System characteristics ********
* curl 7.77.1-DEV (x86_64-pc-linux-gnu)
* libcurl/7.77.1-DEV OpenSSL/1.1.1d
* Features: alt-svc AsynchDNS HSTS HTTPS-proxy IPv6 Largefile NTLM NTLM_WB SSL TLS-SRP UnixSockets
* Disabled:
* Host: debian-kernel
* System: Linux debian-kernel 4.19.0-16-amd64 #1 SMP Debian 4.19.181-1 (2021-03-19) x86_64 GNU/Linux
* OS: linux
* Servers: HTTP-IPv6 HTTP-unix FTP-IPv6
* Env:
* Seed: 231622
*****************************************
test 3020...[HTTP with invalid --connect-to syntax]
-------e--- OK (1   out of 1  , remaining: 00:00, took 1.197s, duration: 00:01)
TESTDONE: 1 tests were considered during 1 seconds.
TESTDONE: 1 tests out of 1 reported OK: 100%

[bagder]

Thanks! (I edited it a little before pushed)