clarify documentation about PTR lookup

Author: dkg

doc/functions.rst

@@ -176,7 +176,7 @@ as its methods and attributes.
    DNS record.  The keyword arguments are:
 
    * ``name``: a representation of the query term; usually a
-     string but must be a dict (as described below) in the
+     string but must be a dict (as described in ``Context.hostname()`` below) in the
      case of a PTR record lookup
    * ``request_type``: a DNS RR type as a getdns constant
      (listed here)
@@ -205,7 +205,7 @@ as its methods and attributes.
 
    * ``address_type``: must be a string matching either "IPv4"
      or "IPv6"
-   * ``address_type``: a string representation of an IPv4 or
+   * ``address_data``: a string representation of an IPv4 or
      IPv6 IP address
 
   .. py:method:: service(name [, extensions], [userarg], [transaction_id], [callback])