(WIP) Fix and enhance logging for port already bound

[michaelortmann]

Found by:
Patch by: michaelortmann
Fixes: #1479

One-line summary:
Fix #1479 by not letting the bot die on .rehash over a changed listen port and enhancing error logging, give the user hints, how to fix it.

Additional description (if needed):

Test cases demonstrating functionality (if applicable):
In eggdrop.conf:
listen 4040 all

.tcl listen 127.0.0.1 4040 all 
[23:21:10] tcl: builtin dcc call: *dcc:tcl -HQ 1 listen 127.0.0.1 4040 all
[23:21:10] tcl: evaluating .tcl listen 127.0.0.1 4040 all
[23:21:10] Listening for telnet connections on 127.0.0.1 port 4040 (all).
[23:21:10] tcl: evaluated .tcl listen 127.0.0.1 4040 all, user 0.031ms sys 0.031ms
Tcl: 4040
.rehash
[23:21:16] tcl: builtin dcc call: *dcc:rehash -HQ 1 
[23:21:16] #-HQ# rehash
Rehashing.
[23:21:16] Writing user file...
[23:21:15] Writing channel file...
[23:21:15] Rehashing ...
[23:21:15] Writing channel file...
[23:21:15] Loading dccwhois.tcl...
[23:21:15] Loaded dccwhois.tcl
[23:21:15] Userinfo TCL v1.08 loaded (URL BF GF IRL EMAIL DOB PHONE ICQ YOUTUBE TWITCH).
[23:21:15] use '.help userinfo' for commands.
[23:21:15] Loaded quotepong.tcl
[23:21:15] Listening for telnet connections on 0.0.0.0 port 3333 (all).
[23:21:15] Listening for telnet connections on 0.0.0.0 port +3343 (all).
[23:21:15] WARNING: Port 4040 is already bound to specific IP 127.0.0.1 on this machine, remove it (using listen [ip] <port> off) before trying to bind to IP 0.0.0.0, check listen settings in config file or restart instead of rehash.
[23:21:15] Writing channel file...
[23:21:15] Userfile loaded, unpacking...