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- Move native txt2iff.c and xpm2iff.c to outdated/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/amiga/amistack.c

@@ -1,5 +1,5 @@
 /* NetHack 3.6	amistack.c	$NHDT-Date: 1432512795 2015/05/25 00:13:15 $  $NHDT-Branch: master $:$NHDT-Revision: 1.8 $ */
-/* Copyright (c) Janne Salmijärvi, Tampere, Finland, 2000		*/
+/* Copyright (c) Janne Salmij�rvi, Tampere, Finland, 2000		*/
 /* NetHack may be freely redistributed.  See license for details.	*/
 
 /*
@@ -12,10 +12,16 @@
 
 #ifdef __SASC_60
 #include <dos.h>
+#endif
 
 /*
- * At the moment 90*1024 would suffice, but just to be on the safe side ...
+ * Increase stack size to allow deep recursions.
+ * NetHack 3.7 with Lua needs significantly more stack than 3.6.
  */
 
-long __stack = 128 * 1024;
+#ifdef __SASC_60
+long __stack = 256 * 1024;
+#else
+/* For GCC with -noixemul (libnix), __stack is also recognized */
+unsigned long __stack = 256 * 1024;
 #endif