Revert "Remove disputed note about read-after-read sync, gh-303"

This reverts commit ec5ca5d5.

pyopencl/array.py

@@ -412,6 +412,12 @@ class Array:
     care of its own operation ordering. The facilities in this section make
     this possible.
 
+    .. note::
+
+        Currently, read and write events are not distinguished.
+        As a result, e.g., read-only operations will needlessly wait on other
+        read-only operations (i.e., executed among asynchronous queues).
+
     .. versionadded:: 2014.1.1
 
     .. attribute:: events