WIP Changes to support building for OS/2

+ WIP Makefile updates to support building for OS/2
   - TODO: Makefile needs SYSNAME test to detect OS/2 (Bill has asked Elbert)
 + Added "__declspec(dllexport)" (via new "TX_EXTERN" #define'd in
   `tp_magic_api.h`) to public function definitions in Magic tools
   - WIP: So far just "Mirror/Flip" plugin
   - TODO: Add "TX_EXTERN" prefix to all other public Magic tool functions
 + Renamed long Magic tool source files to have shorter filenames
   - WIP: So far just "Mirror/Flip" (`mirror_flip.c` -> `mirror_f.c`)
   - TODO: Rename all other magic tool source files.

h/t Elbert Pol for providing info and some diffs!

src/fonts.h

@@ -19,7 +19,7 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   (See COPYING.txt)
 
-  Last updated: June 13, 2023
+  Last updated: June 6, 2024
 */
 
 #ifndef FONTS_H
@@ -28,10 +28,7 @@
 // plan to rip this out as soon as it is considered stable
 //#define THREADED_FONTS
 #define FORKED_FONTS
-#if defined(WIN32) || defined(__BEOS__)
-#undef FORKED_FONTS
-#endif
-#ifdef __ANDROID__
+#if defined(WIN32) || defined(__BEOS__) || defined (__OS2__) || defined(__ANDROID__)
 #undef FORKED_FONTS
 #endif