doc/go1.14: mention Windows change for Open permissions

For #35033

Change-Id: Ie15353322d5cfe7320199103ad9543fb89a842ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/223957
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

doc/go1.14.html

@@ -77,6 +77,18 @@ <h3 id="windows">Windows</h3>
   (Data Execution Prevention)</a> enabled.
 </p>
 
+<p><!-- CL 202439 -->
+  On Windows, creating a file
+  via <a href="/pkg/os#CreateFile"><code>os.OpenFile</code></a> with
+  the <a href="/pkg/os/#O_CREATE"><code>os.O_CREATE</code></a> flag, or
+  via <a href="/pkg/syscall#Open"><code>syscall.Open</code></a> with
+  the <a href="/pkg/syscall#O_CREAT"><code>syscall.O_CREAT</code></a>
+  flag, will now create the file as read-only if the
+  bit <code>0o200</code> (owner write permission) is not set in the
+  permission argument. This makes the behavior on Windows more like
+  that on Unix systems.
+</p>
+
 <h3 id="wasm">WebAssembly</h3>
 
 <p><!-- CL 203600 -->