dns: add resolveAny support

`dns.resolveAny` and `dns.resolve` with `"ANY"` has the similar behavior
like `$ dig <domain> any` and returns an array with several types of
records.

`dns.resolveAny` parses the result packet by several rules in turn.

Supported types:

* A
* AAAA
* CNAME
* MX
* NAPTR
* NS
* PTR
* SOA
* SRV
* TXT

Refs: nodejs#2848

doc/api/dns.md

@@ -197,6 +197,7 @@ records. The type and structure of individual results varies based on `rrtype`:
 | `'SOA'`   | start of authority records     | {Object}    | [`dns.resolveSoa()`][]   |
 | `'SRV'`   | service records                | {Object}    | [`dns.resolveSrv()`][]   |
 | `'TXT'`   | text records                   | {string}    | [`dns.resolveTxt()`][]   |
+| `'ANY'`   | any records                    | {Object}    | [`dns.resolveAny()`][]   |
 
 On error, `err` is an [`Error`][] object, where `err.code` is one of the
 [DNS error codes](#dns_error_codes).
@@ -417,6 +418,51 @@ is a two-dimensional array of the text records available for `hostname` (e.g.,
 one record. Depending on the use case, these could be either joined together or
 treated separately.
 
+## dns.resolveAny(hostname, callback)
+
+- `hostname` {string}
+- `callback` {Function}
+  - `err` {Error}
+  - `ret` {Object[][]}
+
+Uses the DNS protocol to resolve any queries (`ANY` records) for the `hostname`.
+The `ret` argument passed to the `callback` function will be an array of objects
+with uncertain type of records. Each object has a property `type` that indicates
+the type of current record. And for each type of record, the object structure
+will be like:
+
+| Type | Properties |
+|------|------------|
+| `"A"` | `address` / `ttl` |
+| `"AAAA"` | `address` / `ttl` |
+| `"CNAME"` | `value` |
+| `"MX"` | Refer to [`dns.resolveMx()`][] |
+| `"NAPTR"` | Refer to [`dns.resolveNaptr()`][] |
+| `"NS"` | `value` |
+| `"PTR"` | `value` |
+| `"SOA"` | Refer to [`dns.resolveSoa()`][] |
+| `"SRV"` | Refer to [`dns.resolveSrv()`][] |
+| `"TXT"` | This is an array-liked object with `length` and `indexes`, eg. `{'0':'sth','length':1}` |
+
+Following is a example of the `ret` object passed to the callback:
+
+<!-- eslint-disable -->
+```js
+[ { address: '127.0.0.1', ttl: 299, type: 'A' },
+  { value: 'example.com', type: 'CNAME' }, // in fact, CNAME can't stay with A
+  { exchange: 'alt4.aspmx.l.example.com', priority: 50, type: 'MX' },
+  { value: 'ns1.example.com', type: 'NS' },
+  { '0': 'v=spf1 include:_spf.example.com ~all', type: 'TXT', length: 1 },
+  { nsname: 'ns1.example.com',
+    hostmaster: 'admin.example.com',
+    serial: 156696742,
+    refresh: 900,
+    retry: 900,
+    expire: 1800,
+    minttl: 60,
+    type: 'SOA' } ]
+```
+
 ## dns.reverse(ip, callback)
 <!-- YAML
 added: v0.1.16
@@ -531,6 +577,7 @@ uses. For instance, _they do not use the configuration from `/etc/hosts`_.
 [`dns.resolveSoa()`]: #dns_dns_resolvesoa_hostname_callback
 [`dns.resolveSrv()`]: #dns_dns_resolvesrv_hostname_callback
 [`dns.resolveTxt()`]: #dns_dns_resolvetxt_hostname_callback
+[`dns.resolveAny()`]: #dns_dns_resolveany_hostname_callback
 [DNS error codes]: #dns_error_codes
 [Implementation considerations section]: #dns_implementation_considerations
 [supported `getaddrinfo` flags]: #dns_supported_getaddrinfo_flags

lib/dns.js

@@ -279,6 +279,7 @@ function resolver(bindingName) {
 
 
 var resolveMap = Object.create(null);
+resolveMap.ANY = resolver('queryAny');
 resolveMap.A = resolver('queryA');
 resolveMap.AAAA = resolver('queryAaaa');
 resolveMap.CNAME = resolver('queryCname');
@@ -361,6 +362,7 @@ module.exports = {
   getServers,
   setServers,
   resolve,
+  resolveAny: resolveMap.ANY,
   resolve4: resolveMap.A,
   resolve6: resolveMap.AAAA,
   resolveCname: resolveMap.CNAME,