src: nix stdin _readableState.reading manipulation

this opts for stream.push('') which has the same effect
but uses a public API.

PR-URL: #454
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>

src/node.js

@@ -699,7 +699,7 @@
       // not-reading state.
       if (stdin._handle && stdin._handle.readStop) {
         stdin._handle.reading = false;
-        stdin._readableState.reading = false;
+        stdin.push('');
         stdin._handle.readStop();
       }
 
@@ -708,7 +708,7 @@
       stdin.on('pause', function() {
         if (!stdin._handle)
           return;
-        stdin._readableState.reading = false;
+        stdin.push('');
         stdin._handle.reading = false;
         stdin._handle.readStop();
       });