fs: re-enable watch facility in AIX

doc/api/fs.md

@@ -1750,6 +1750,13 @@ a new inode. The watch will emit an event for the delete but will continue
 watching the *original* inode. Events for the new inode will not be emitted.
 This is expected behavior.
 
+In AIX, save and close of a file being watched causes two notifications -
+one for adding new content, and one for truncation. Moreover, save and 
+close operations on some platforms cause inode changes that force watch 
+operations to become invalid and ineffective. AIX retains inode for the 
+lifetime of a file, that way though this is different from Linux / OS X, 
+this improves the usability of file watching. This is expected behavior.
+
 #### Filename Argument
 
 <!--type=misc-->

test/parallel/parallel.status

@@ -18,10 +18,3 @@ prefix parallel
 
 [$system==freebsd]
 
-# fs-watch currently needs special configuration on AIX and we
-# want to improve under https://github.com/nodejs/node/issues/5085.
-# Tests are disabled so CI can be green and we can spot other
-# regressions until this work is complete
-[$system==aix]
-test-fs-watch-enoent                 : FAIL, PASS
-test-fs-watch-encoding               : FAIL, PASS

test/parallel/test-fs-watch-encoding.js

@@ -14,6 +14,15 @@ const common = require('../common');
 const fs = require('fs');
 const path = require('path');
 
+// fs-watch on folders have limited capability in AIX.
+// The testcase makes use of folder watching, and causes
+// hang. This behavior is documented. Skip this for AIX.
+
+if (common.isAix) {
+  common.skip('folder watch capability is limited in AIX.');
+  return;
+}
+
 common.refreshTmpDir();
 
 const fn = '新建文夹件.txt';