Fix net/rtg with modern perl and php

• Fix runtime PHP errors if short_opentag is disabled (default)
• Remove most PHP warnings/notices that go to error_log
• Fix HTML output to be valid
• Fix quoting of SQL objects
• Fix escaping of user-provided SQL data (potential sql injection)
• Widen fields in 95.php and 95.pl for interface and router names
• Fix warnings in perl modules in newer perl versions
• Fix createdb script to use CREATE USER/GRANT not manipulate user db directly
• Add "Update_desc" config entry to auto-update port descriptions from snmp
• Update default SNMP version to 2

PR: 227376
Submitted by: <freebsd-ports@dan.me.uk> (maintainer)