rad_counter: Use heredoc for help message

Use Perl's here document syntax for rad_counter's help message and
replace tab escape sequences with spaces to make the source more
readable and easier to modify.
rad_counter: Refine help message

Refine rad_counter help message:

* use executable name without path,
* add program purpose,
* shorten usage summary line for clarity,
* separate arguments and options,
* add full stops to sentences,
* wrap a long line.
dhcpclient: Add a short description to help output

Add a short description of the program's function to the help output of
dhcpclient.
Fix coa_separate to behave differently for proxy reply
Fix bad VP array type value accesses
Typo
Remove &Attr[#] it's very difficult to make it work correctly everywhere
Typo
Zero log.indent in child requests
Add more EVAL_DEBUG statements so we can determine source of normalisation type
Remove restriction on implicit casts in map_to_vp
Add code to convert between IPv4/v6 addresses and IPv4/v6 prefixes
Formatting
Avoid shift overflow that cause incorrect masking to be applied to /64 prefixes
Remove unused code
Error out if the attribute is unknown after pass2
raddb: Move trigger.conf INCLUDE before modules

Move "$INCLUDE trigger.conf" chunk before module section in
"radiusd.conf.in". This makes it possible to reference "snmptrap" and
related trigger variables under "pool.trigger" in module configurations,
simplifying them.

E.g. like this (in raddb/mods-enabled/ldap):

ldap ldap_instance {
    pool {
        trigger {
            args = "radiusdModuleName s '${...:name}' radiusdModuleInstance s '${...:instance}'"
            open = "${snmptrap}::serverModuleConnectionUp ${args}"
            close = "${snmptrap}::serverModuleConnectionDown ${args}"
        }
    }
}
Better way of dealing with undefined attrs in update
Add explicit tests for unknown in condition
Typo