pinky: disable location canonicalization by default

Behave like who(1) in requiring --lookup to enable this
often slow feature.  pinky(1) is supposed to be lightweight after all.

* doc/coreutils.texi (who invocation): Adjust the description to no
longer reference dialup, and be more general about the still significant
delays.
(pinky invocation): Reference the same --lookup description.
* src/pinky.c (main): Accept --lookup to enable DNS lookups.
* NEWS: Mention the change in behavior.
Fixes https://bugs.debian.org/628815

doc/coreutils.texi

@@ -16203,11 +16203,13 @@ Print a line of column headings.
 List only the entries that correspond to processes via which the
 system is waiting for a user to login.  The user name is always @samp{LOGIN}.
 
+@macro lookupOption
 @item --lookup
 @opindex --lookup
-Attempt to canonicalize hostnames found in utmp through a DNS lookup.  This
-is not the default because it can cause significant delays on systems with
-automatic dial-up internet access.
+Attempt to canonicalize hostnames found in utmp through a DNS lookup.
+This is not the default because of potential delays.
+@end macro
+@lookupOption
 
 @item -m
 @opindex -m
@@ -16335,6 +16337,8 @@ format.
 Omit the user's full name, remote host, and idle time when printing in
 short format.
 
+@lookupOption
+
 @end table
 
 @exitstatus