Bump to 0.9.24; improve usage output

Bumping to 0.9.24; going to add a new feature momentarily.

Improved usage output (e.g., that of "tuxpaint --help"); broke
the options into groups that match the tabs in Tux Paint Config.,
added some missing options.

docs/CHANGES.txt

@@ -8,7 +8,7 @@ http://www.tuxpaint.org/
 
 $Id$
 
-2018.Oct.7 (0.9.23c)
+2018.Dec.18 (0.9.24)
   * Bug Fixes
     ---------
     * Correct issue that prevented Tux Paint from lauching on Mac OS X 10.7.
@@ -31,6 +31,8 @@ $Id$
     * Mended link to MinGW/MSYS instructions at John Popplewell's website.
       (h/t "sechidis")
 
+    * Improved and expanded usage info (e.g., "tuxpaint --help" output)
+
   * Misc
     ----
     * Verbose debugging, and "DEBUG_PRINTF()" macro now available;

docs/en/README.txt

@@ -1,12 +1,12 @@
                                    Tux Paint
-                                version 0.9.23c
+                                 version 0.9.24
 
   A simple drawing program for children
 
           Copyright 2002-2018 by various contributors; see AUTHORS.txt
                             http://www.tuxpaint.org/
 
-                        June 14, 2002 - October 7, 2018
+                       June 14, 2002 - December 18, 2018
 
      ----------------------------------------------------------------------
 

docs/en/html/README.html

@@ -12,7 +12,7 @@ alt="Tux&nbsp;Paint"><br>
 
 version
 
-0.9.23c
+0.9.24
 
 </h1>
 <h3>A simple drawing program for children</h3>
@@ -22,7 +22,7 @@ version
 
 <p>June 14, 2002 -
 
-				October 7, 2018</p>
+				December 18, 2018</p>
 
 </center>