bpo-37039: Make IDLE's Zoom Height adjust to users' screens (GH-13678)

Measure required height by quickly maximizing once per screen.
A search for a better method failed.
diff --git a/Lib/idlelib/help.html b/Lib/idlelib/help.html
index 228b319..e27ec8d 100644
--- a/Lib/idlelib/help.html
+++ b/Lib/idlelib/help.html
@@ -6,7 +6,7 @@
   <head>
     <meta http-equiv="X-UA-Compatible" content="IE=Edge" />
     <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
-    <title>IDLE &#8212; Python 3.8.0a4 documentation</title>
+    <title>IDLE &#8212; Python 3.9.0a0 documentation</title>
     <link rel="stylesheet" href="../_static/pydoctheme.css" type="text/css" />
     <link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
 
@@ -19,7 +19,7 @@
     <script type="text/javascript" src="../_static/sidebar.js"></script>
 
     <link rel="search" type="application/opensearchdescription+xml"
-          title="Search within Python 3.8.0a4 documentation"
+          title="Search within Python 3.9.0a0 documentation"
           href="../_static/opensearch.xml"/>
     <link rel="author" title="About these documents" href="../about.html" />
     <link rel="index" title="Index" href="../genindex.html" />
@@ -50,6 +50,7 @@
 
 
   </head><body>
+
     <div class="related" role="navigation" aria-label="related navigation">
       <h3>Navigation</h3>
       <ul>
@@ -72,7 +73,7 @@
 
 
     <li>
-      <a href="../index.html">3.8.0a4 Documentation</a> &#187;
+      <a href="../index.html">3.9.0a0 Documentation</a> &#187;
     </li>
 
           <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
@@ -320,7 +321,10 @@
 <dt>Zoom/Restore Height</dt>
 <dd>Toggles the window between normal size and maximum height. The initial size
 defaults to 40 lines by 80 chars unless changed on the General tab of the
-Configure IDLE dialog.</dd>
+Configure IDLE dialog.  The maximum height for a screen is determined by
+momentarily maximizing a window the first time one is zoomed on the screen.
+Changing screen settings may invalidate the saved height.  This toogle has
+no effect when a window is maximized.</dd>
 </dl>
 </div>
 <div class="section" id="window-menu-shell-and-editor">
@@ -912,7 +916,7 @@
 
 
     <li>
-      <a href="../index.html">3.8.0a4 Documentation</a> &#187;
+      <a href="../index.html">3.9.0a0 Documentation</a> &#187;
     </li>
 
           <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
@@ -943,7 +947,7 @@
 <br />
     <br />
 
-    Last updated on May 25, 2019.
+    Last updated on Jun 17, 2019.
     <a href="https://docs.python.org/3/bugs.html">Found a bug</a>?
     <br />