doc: doc that listen can be called multiple times

Fixes: https://github.com/nodejs/node/issues/4646
PR-URL: https://github.com/nodejs/node/pull/8294
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/http.md

@@ -681,6 +681,9 @@ This function is asynchronous. `callback` will be added as a listener for the
 
 Returns `server`.
 
+*Note*: The `server.listen()` method may be called multiple times. Each
+subsequent call will *re-open* the server using the provided options.
+
 ### server.listen(path[, callback])
 <!-- YAML
 added: v0.1.90
@@ -691,6 +694,9 @@ Start a UNIX socket server listening for connections on the given `path`.
 This function is asynchronous. `callback` will be added as a listener for the
 [`'listening'`][] event.  See also [`net.Server.listen(path)`][].
 
+*Note*: The `server.listen()` method may be called multiple times. Each
+subsequent call will *re-open* the server using the provided options.
+
 ### server.listen([port][, hostname][, backlog][, callback])
 <!-- YAML
 added: v0.1.90
@@ -713,6 +719,9 @@ parameter is 511 (not 512).
 This function is asynchronous. `callback` will be added as a listener for the
 [`'listening'`][] event.  See also [`net.Server.listen(port)`][].
 
+*Note*: The `server.listen()` method may be called multiple times. Each
+subsequent call will *re-open* the server using the provided options.
+
 ### server.listening
 <!-- YAML
 added: v5.7.0

doc/api/net.md

@@ -173,6 +173,9 @@ server.listen({
 });
 ```
 
+*Note*: The `server.listen()` method may be called multiple times. Each
+subsequent call will *re-open* the server using the provided options.
+
 ### server.listen(path[, backlog][, callback])
 <!-- YAML
 added: v0.1.90
@@ -210,6 +213,9 @@ double-backslashes, such as:
 The parameter `backlog` behaves the same as in
 [`server.listen([port][, hostname][, backlog][, callback])`][`server.listen(port, host, backlog, callback)`].
 
+*Note*: The `server.listen()` method may be called multiple times. Each
+subsequent call will *re-open* the server using the provided options.
+
 ### server.listen([port][, hostname][, backlog][, callback])
 <!-- YAML
 added: v0.1.90
@@ -249,6 +255,9 @@ server.on('error', (e) => {
 
 (Note: All sockets in Node.js are set `SO_REUSEADDR`.)
 
+*Note*: The `server.listen()` method may be called multiple times. Each
+subsequent call will *re-open* the server using the provided options.
+
 ### server.listening
 <!-- YAML
 added: v5.7.0