Revert lost translations in es, gl, ja

Looks like Jacques needs to enable these locales on his system.

docs/ja_JP.UTF-8/html/PNG.html

@@ -17,16 +17,16 @@
             width="205"
             height="210"
             alt="Tux Paint"><br>
-        version 0.9.27<br/>
+        バージョン 0.9.27<br/>
         PNG Documentation      </h1>
 
       <p>
-        Copyright &copy; 2007-2021 by various contributors; see AUTHORS.<br>
+        Copyright &copy; 2007-2021 by various contributors; "AUTHORS" 参照.<br>
         <a href="http://www.tuxpaint.org/">http://www.tuxpaint.org/</a>
       </p>
 
       <p>
-        March  9, 2021      </p>
+        2021年3月 9日      </p>
     </center>
 
     <hr>
@@ -69,7 +69,7 @@
       The "cjpeg" and "djpeg" command-line programs convert between the NetPBM Portable Any Map (PNM) format and JPEGs.
       It is possible that it's already installed on your system. If not, they it be readily available from your Linux distribution's software repository.  If not, or to learn more, visit <a href="https://jpegclub.org/">https://jpegclub.org/</a>.    </p>
 
-    <h3>Windows Users</h3>
+    <h3>Windows のユーザー</h3>
     <ul>
       <li>  <cite>CorelDRAW</cite>
   (Corel)