Revive Amiga port for NetHack 3.7

Update the Amiga Intuition window port (AMII/AMIV) for the 3.7
window_procs API. Key changes:

- Update all window function signatures for 3.7
- Add assembly trampolines for AmigaOS register-based callbacks
- Convert all K&R function definitions to C99
- Add cross-compilation build system (cross-pre1/pre2/post.370)
  using bebbo's m68k-amigaos-gcc with -noixemul -std=gnu17 -m68000
- Clipping fixes: viewport centering, simplified ScrollRaster,
  duplicate Ctrl-R suppression, glyph buffer invalidation
- Add menucolor support in menu rendering
- Move native txt2iff.c and xpm2iff.c to outdated/
- Add nethack.cnf and README.amiga

sys/share/pcmain.c

@@ -128,6 +128,7 @@ _CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDERR);*/
 
     choose_windows(DEFAULT_WINDOW_SYS);
 
+
 #if !defined(AMIGA) && !defined(GNUDOS)
     /* Save current directory and make sure it gets restored when
      * the game is exited.
@@ -147,6 +148,10 @@ _CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDERR);*/
     if (dir == (char *) 0)
         dir = exepath(argv[0]);
 #endif
+#if defined(AMIGA) && defined(HACKDIR)
+    if (dir == (char *) 0)
+        dir = HACKDIR;
+#endif
 #ifdef _MSC_VER
     if (IsDebuggerPresent()) {
         static char exepath[_MAX_PATH];