fix location for tuxpaint.cfg on Haiku

Unclear why when I `git pull` in master, I'm not seeing
https://sourceforge.net/p/tuxpaint/tuxpaint/ci/b48cb438239e47ebce3c6b84f5aff2d7d906d3ba/
so just replicating it (plus adding entry to docs/CHANGES.txt).

docs/CHANGES.txt

@@ -6,7 +6,7 @@ Copyright (c) 2002-2023
 Various contributors (see below, and AUTHORS.txt)
 https://tuxpaint.org/
 
-2023.May.10 (0.9.30)
+2023.May.12 (0.9.30)
   * Improvements to Stamp tool:
     ---------------------------
     * Avoid playing English descriptive sound for a stamp
@@ -149,6 +149,10 @@ https://tuxpaint.org/
       (e.g. 90 and 91), where 'garbage' graphics could appear.
       Bill Kendrick <bill@newbreedsoftware.com>
 
+    * On Haiku, read config from the correct location
+      ({home}/config/settings/TuxPaint/tuxpaint.cfg)
+      Luc 'Begasus' Schrijvers <begasus@gmail.com>
+
   * Ports & Building:
     -----------------
     * Created "src/indent.sh", to run 'indent' against source files.

src/tuxpaint.c

@@ -22,7 +22,7 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   (See COPYING.txt)
 
-  June 14, 2002 - May 10, 2023
+  June 14, 2002 - May 12, 2023
 */
 
 #include "platform.h"
@@ -27661,7 +27661,7 @@ static void setup_config(char *argv[])
   safe_snprintf(str, sizeof(str), "%s/tuxpaint.cfg", savedir);  /* FIXME */
 #elif defined(__BEOS__) || defined(__HAIKU__)
   /* BeOS: Use a "tuxpaint.cfg" file: */
-  strcpy(str, "tuxpaint.cfg");  /* safe; sufficient size */
+  safe_snprintf(str, sizeof(str), "%s/config/settings/TuxPaint/tuxpaint.cfg", home);
 #elif defined(__APPLE__)
   /* macOS, iOS: Use a "tuxpaint.cfg" file in the Tux Paint application support folder */
   safe_snprintf(str, sizeof(str), "%s/tuxpaint.cfg", apple_preferencesPath());