add cross-compile recipe for amiga

Disclaimer: This is a minimal recipe, just to get someone else
started if they have a desire to get a full cross-compile of
NetHack-3.7 going for the Amiga. Some NetHack code bitrot was
corrected, and it does seem able to compile the game itself
to a point. See caveats below.

- If you want to obtain the cross-compiler and tools/libs for Amiga
         https://github.com/bebbo/amiga-gcc

  To our knowledge, a pre-built copy isn't available, so you have to
  obtain the source via git and build it on your system.

  The build prerequisite packages for Ubuntu are easily obtained:

    sudo apt install make wget git gcc g++ lhasa libgmp-dev \
        libmpfr-dev libmpc-dev flex bison gettext texinfo ncurses-dev \
        autoconf rsync

  The build prerequisite packages for macOS are apparently easily
  obtained via homebrew, but that was not tested:

    brew install bash wget make lhasa gmp mpfr libmpc flex gettext \
    texinfo gcc make autoconf

  After installing the prerequite packages and the cross-compiler
  it was a straightforward build:

        git clone https://github.com/bebbo/amiga-gcc.git
        cd amiga-gcc
        make update
    [Note that you may have to take ownership of the files in the
     bebbo repo via chown before succesfully carrying out the next
     steps]
        make clean
        make clean-prefix
        date; make all -j3 >&b.log; date
  The compiler pieces are installed in /opt/amiga by default which
  was satisfactory for our initial attempt, but if you want you can
  alter the prefix before you build if you want. That is all
  spelled out on the page at: https://github.com/bebbo/amiga-gcc

  The Amiga cross-compile can then be carried out by specifying
  CROSS_TO_AMIGA=1 on the make command line.

  For example:
       make CROSS_TO_AMIGA=1 all
       make CROSS_TO_AMIGA=1 package

You can explicitly include tty and curses support if desired, otherwise
you'll end up with a tty-only cross-compile build. The SDL1 pdcurses
support has not been tested.

       make WANT_WIN_TTY=1 WANT_WIN_CURSES=1 CROSS_TO_AMIGA=1 all

Also note that building the amiga targets using the make command
above, does not preclude you from building local linux or macOS
targets as well. Just drop the CROSS_TO_AMIGA=1 from the make
command line.

The cross-compiler hints additions are enclosed inside ifdef sections
and won't interfere with the non-cross-compile build in that case.

CAVEATS: The original NetHack Amiga build steps included the source for
some utilities that were built and executed on the amiga: txt2iff and
xpm2iff as part of the NetHack build procedure on amiga. Those did not
compile out-of-the-box on the linux host. They will either have to be:
    - ported to build and run on the linux or macOS cross-compile host

   or

    - their functionality will have to be rolled into amiga NetHack
      itself and executed on the target Amiga the first time the game
      is run, perhaps.

Good luck amiga aficionados, perhaps you'll be able to take this
initial effort forward and get NetHack-3.7 available on the amiga or
amiga-emulator. Let us know if you do, and we can roll changes in
if you provide them.

outdated/include/amiconf.h

@@ -14,6 +14,11 @@
 
 #include <time.h> /* get time_t defined before use! */
 
+#ifdef AMIGA_CROSS
+#include <stdlib.h>
+#include <string.h>
+#endif
+
 #ifdef __SASC_60    /* since SAS can prevent re-inclusion */
 #include <stdlib.h> /* general things, including builtins */
 #include <string.h>
@@ -40,6 +45,8 @@ typedef long off_t;
                              LEVELDIR, SAVEDIR, BONESDIR, DATADIR,    \
                              SCOREDIR, LOCKDIR, CONFIGDIR, and TROUBLEDIR */
 
+#define PATHLEN 130
+
 /* data librarian defs */
 #ifndef NOCWD_ASSUMPTIONS
 #define DLBFILE "NetHack:nhdat"   /* main library */
@@ -49,7 +56,11 @@ typedef long off_t;
 #define DLBFILE2 "nhsdat" /* sound library */
 #endif
 
+#ifndef AMIGA_CROSS
 #define FILENAME_CMP stricmp /* case insensitive */
+#else
+#define FILENAME_CMP strcmpi /* case insensitive */
+#endif
 
 #ifndef __SASC_60
 #define O_BINARY 0
@@ -65,7 +76,9 @@ typedef long off_t;
 #define MFLOPPY /* You'll probably want this; provides assistance \
                  * for typical personal computer configurations   \
                  */
+#ifndef AMIGA_CROSS
 #define RANDOM
+#endif
 
 /* ### amidos.c ### */
 
@@ -123,8 +136,6 @@ extern FILE *FDECL(freopen, (const char *, const char *, FILE *));
 extern char *FDECL(gets, (char *));
 #endif
 
-#define msmsg printf
-
 /*
  * If AZTEC_C  we can't use the long cpath in vision.c....
  */
@@ -138,7 +149,9 @@ extern char *FDECL(gets, (char *));
 
 #define TEXTCOLOR /* Use colored monsters and objects */
 #define HACKFONT  /* Use special hack.font */
-#define SHELL     /* Have a shell escape command (!) */
+#ifndef AMIGA_CROSS   /* issues with prototype and spawnl */
+#define SHELL  /* Have a shell escape command (!) */
+#endif
 #define MAIL      /* Get mail at unexpected occasions */
 #define DEFAULT_ICON "NetHack:default.icon" /* private icon */
 #define AMIFLUSH /* toss typeahead (select flush in .cnf) */
@@ -186,5 +199,24 @@ void FDECL(amii_setpens, (int));
 #undef M
 #define M(c) ((c) -128)
 #endif
+struct ami_sysflags {
+	char sysflagsid[10];
+#ifdef AMIFLUSH
+	boolean altmeta;  /* use ALT keys as META */
+	boolean amiflush; /* kill typeahead */
+#endif
+#ifdef AMII_GRAPHICS	        
+	int numcols;
+	unsigned short amii_dripens[20]; /* DrawInfo Pens currently there are 13 in v39 */
+	AMII_COLOR_TYPE amii_curmap[AMII_MAXCOLORS]; /* colormap */
+#endif
+#ifdef OPT_DISPMAP
+	boolean fast_map; /* use optimized, less flexible map display */
+#endif
+#ifdef MFLOPPY
+	boolean asksavedisk;
+#endif
+};
+extern struct ami_sysflags sysflags;
 
 #endif /* AMICONF_H */