Allow gen_nb_server to use IPv6 addresses.

[seancribbs]

This supersedes #245, supporting both tuple and string-formatted addresses, and cleans up extraneous whitespace in the file.

[evanmcc]

shouldn't there be a catchall case here for when none of the guarded versions are satisfied, throwing an error?

[seancribbs]

Good call, adding.

[slfritchie]

+1 to merge, thanks!

I used the diff below to verify that the HTTP listener, PB listener, and handoff listener are all using IPv6. Note that the distributed Erlang ports are still using IPv4.

% lsof -nP -p 34359 | grep TCP
beam.smp 34359 fritchie   12u    IPv4 0x689ef020065f186d       0t0      TCP *:50005 (LISTEN)
beam.smp 34359 fritchie   13u    IPv4 0x689ef0200273386d       0t0      TCP 127.0.0.1:50006->127.0.0.1:4369 (ESTABLISHED)
beam.smp 34359 fritchie   19u    IPv6 0x689ef01fffeba72d       0t0      TCP [::1]:8099 (LISTEN)
beam.smp 34359 fritchie   20u    IPv6 0x689ef01fffeba34d       0t0      TCP [::1]:8098 (LISTEN)
beam.smp 34359 fritchie   21u    IPv6 0x689ef02014422b0d       0t0      TCP [::1]:8087 (LISTEN)

Diff:

--- rel/riak/etc/vm.args.orig   2012-11-13 11:24:58.000000000 -0600
+++ rel/riak/etc/vm.args    2012-11-13 11:25:09.000000000 -0600
@@ -1,5 +1,5 @@
 ## Name of the riak node
--name riak@127.0.0.1
+-name riak@::1

 ## Cookie for distributed erlang.  All nodes in the same cluster
 ## should use the same cookie or they will not be able to communicate.
--- rel/riak/etc/app.config.orig    2012-11-13 11:24:57.000000000 -0600
+++ rel/riak/etc/app.config 2012-11-13 11:29:34.000000000 -0600
@@ -12,7 +12,7 @@

             %% pb_ip is the IP address that the Riak Protocol Buffers interface
             %% will bind to.  If this is undefined, the interface will not run.
-            {pb_ip,   "127.0.0.1" },
+            {pb_ip,   "::1" },

             %% pb_port is the TCP port that the Riak Protocol Buffers interface
             %% will bind to
@@ -30,11 +30,11 @@

               %% http is a list of IP addresses and TCP ports that the Riak
               %% HTTP interface will bind.
-              {http, [ {"127.0.0.1", 8098 } ]},
+              {http, [ {"::1", 8098 } ]},

               %% https is a list of IP addresses and TCP ports that the Riak
               %% HTTPS interface will bind.
-              %{https, [{ "127.0.0.1", 8098 }]},
+              %{https, [{ "::1", 8098 }]},

               %% Default cert and key locations for https can be overridden
               %% with the ssl config variable, for example:
@@ -45,6 +45,7 @@

               %% riak_handoff_port is the TCP port that Riak uses for
               %% intra-cluster data handoff.
+              {handoff_ip, "::1"},
               {handoff_port, 8099 },

               %% To encrypt riak_core intra-cluster data handoff traffic,