[exim] Request for actual rDNS variable

I'm aware of alternatives/workarounds to what I'm requesting, so no
need to rehash them....

I would like to see a variable in exim that reflects the actual rDNS
value for sender_host_address.

Properly I think sender_host_name should have that value and there
should be a new variable, perhaps sender_host_name_verified that
contains the result of reverse AND forward lookups on
sender_host_address.

Given backward compatibility concerns, perhaps just a new variable:
sender_host_rdns would suffice.


Regards,
Brian