doc: update docs with AIX related information

Fixes: https://github.com/libuv/libuv/issues/882
PR-URL: https://github.com/libuv/libuv/pull/896
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

docs/src/fs.rst

@@ -258,6 +258,10 @@ API
 
     Equivalent to :man:`utime(2)` and :man:`futime(2)` respectively.
 
+    .. note::
+      AIX: This function only works for AIX 7.1 and newer. It can still be called on older
+      versions but will return ``UV_ENOSYS``.
+
     .. versionchanged:: 1.10.0 sub-second precission is supported on Windows
 
 .. c:function:: int uv_fs_link(uv_loop_t* loop, uv_fs_t* req, const char* path, const char* new_path, uv_fs_cb cb)

docs/src/fs_event.rst

@@ -8,6 +8,20 @@ FS Event handles allow the user to monitor a given path for changes, for example
 if the file was renamed or there was a generic change in it. This handle uses
 the best backend for the job on each platform.
 
+.. note::
+    For AIX, the non default IBM bos.ahafs package has to be installed.
+    The AIX Event Infrastructure file system (ahafs) has some limitations:
+
+        - ahafs tracks monitoring per process and is not thread safe. A separate process
+          must be spawned for each monitor for the same event.
+        - Events for file modification (writing to a file) are not received if only the
+          containing folder is watched.
+
+    See documentation_ for more details.
+
+    .. _documentation: http://www.ibm.com/developerworks/aix/library/au-aix_event_infrastructure/
+
+
 
 Data types
 ----------