Vendor the Shockolate engine and build it via a Docker image with every

dependency (SDL2, SDL2_mixer, fluidsynth-lite, a MIDI soundfont)
prebuilt, so compiling the engine needs no network access - just the
image and the engine source. Add res/assets/extract_assets.sh to pull
the game's data files out of a purchased GOG installer, and a Makefile
that assembles a runnable dist/ from the two.

Also add `make package`, which builds a redistributable tarball that
omits the proprietary game assets (shipping res/GET_ASSETS.txt instead)
plus license information for both the MIT tooling and the GPLv3 engine,
and a Gitea Actions workflow that builds and publishes it to
dl.ladkau.de on every push.

engine/src/GameSrc/Headers/amap.h

@@ -0,0 +1,123 @@
+/*
+
+Copyright (C) 2015-2018 Night Dive Studios, LLC.
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+#ifndef __AMAP_H
+#define __AMAP_H
+
+// header for the real infernal automap
+
+// defines
+#define AMAP_PURE_MODE 0x0000
+#define AMAP_INT_WALLS 0x0001
+#define AMAP_SHOW_CRIT 0x0002
+#define AMAP_SHOW_ROB  0x0004
+#define AMAP_SHOW_HAZ  0x0008
+#define AMAP_SHOW_FLR  0x0010
+#define AMAP_SHOW_MSG  0x0020
+#define AMAP_SHOW_HGT  0x0040
+#define AMAP_TRACK_OBJ 0x0080
+#define AMAP_SHOW_SEC  0x0100
+#define AMAP_FULL_MSG  0x0200
+#define AMAP_SHOW_ALL  0x0400
+#define AMAP_SHOW_SENS 0x0800
+
+#define AMAP_AVAIL_ALWAYS (AMAP_SHOW_SENS | AMAP_SHOW_FLR | AMAP_FULL_MSG)
+
+#define AMAP_SET       1
+#define AMAP_UNSET     0
+#define AMAP_TOGGLE   -1
+
+#define AMAP_PAN_N     1
+#define AMAP_PAN_E     2
+#define AMAP_PAN_S     3
+#define AMAP_PAN_W     4
+#define AMAP_DEF_DST   0x40000
+
+#define AMAP_MAX_ZOOM  6
+#define AMAP_MIN_ZOOM  1
+
+#define AMAP_OFF_MAP   0
+#define AMAP_HAVE_NOTE 1
+#define AMAP_NO_NOTE   2
+
+// really should live in the player structure....
+typedef struct {
+    uchar init;
+    uchar zoom;
+    int xf, yf;
+    ushort lw, lh;
+    ushort obj_to_follow, sensor_obj;
+    ushort note_obj;
+    ushort flags;
+    ushort avail_flags;
+    uchar version_id;
+    ushort sensor_rad; // in obj coords
+} curAMap;
+
+// prototypes
+uchar amap_kb_callback(curAMap *amptr, int code);
+void amap_draw(curAMap *amptr, int expose);
+void amap_version_set(int id, int new_ver);
+void automap_init(int version, int id);
+void amap_invalidate(int id);
+uchar amap_flags(curAMap *amptr, int flags, int set);                  // set -1 to toggle
+uchar amap_zoom(curAMap *amptr, uchar set, int zoom_delta);
+void amap_pan(curAMap *amptr, int dir, int *dist);
+uchar amap_get_note(curAMap *amptr, char *buf);
+void amap_pixratio_set(fix ratio);
+void amap_settings_copy(curAMap *from, curAMap *to);
+
+grs_bitmap *screen_automap_bitmap(char which_amap);
+
+// this is a mess
+// it modifies x and y to be map location of click
+// returns null if off map, (void*)mapelemptr if within map
+// sets amptr->note_obj to the note if found, else OBJ_NULL
+void *amap_deal_with_map_click(curAMap *amptr, int *x, int *y);
+
+// strings
+void amap_str_init(void);
+char *amap_str_next(void);
+void amap_str_grab(char *str);
+int amap_str_deref(char *str);
+char *amap_str_reref(int offs);
+void amap_str_delete(char *toast_str);
+void amap_str_startup(int magic_num);
+
+#define MFD_FULLSCR_MAP 2
+#define NUM_O_AMAP MFD_FULLSCR_MAP + 1
+
+// globals
+// for now
+
+#define oAMap(mid) (&(level_gamedata.auto_maps[mid]))
+//#define oAMap(mid) (auto_maps[mid])
+
+#define amap_reset()                     \
+    do {                                 \
+        int i;                           \
+        for (i = 0; i < NUM_O_AMAP; i++) \
+            amap_invalidate(i);          \
+    } while (0)
+
+#define amap_note_value(objid)  (objTraps[objs[objid].specID].p4)
+#define amap_note_string(objid) (amap_str_reref(amap_note_value(objid)))
+
+#define AMAP_STRING_SIZE 2048
+
+#endif