libnethack pr385

roll parts of pr385 into source tree

This does not take the PR as is.

Unlike the PR, this streamlines and minimizes the integration somewhat:

- use hints/include mechanism instead of creating alternative
  Makefile.dat, Makefile.src, Makefile.top, Makefile.utl in sys/lib;
  those would have been a maintenance nightmare.

- don't have alternative mkmkfile.sh and setup.sh in sys/lib.

- sys/lib/libnethackmain.c differed from sys/unix/unixmain.c by
  very little, so just place a small bit of conditional code at the
  top of sys/unix/unixmain.c instead.

- changed the conditional code bits from __EMSCRIPTEN__ to
  CROSS_TO_WASM.

- You should be able to build the wasm result by:
    cd sys/unix ; sh setup.sh hints/linux.2020 ; cd ../..
    make fetch-lua    (<-one time)
    make WANT_LIBNH all

- You should be able to build LIBNBH by:
    cd sys/unix ; sh setup.sh hints/linux.2020 ; cd ../..
    make fetch-lua    (<-one time)
    make CROSS_TO_WASM=1 all

As it is currently coded, winshim.c requires C99.

sys/lib/npm-package/src/nethackShim.js

@@ -0,0 +1,49 @@
+const path = require("path");
+
+let Module;
+let userCallback;
+let savedOnRuntimeInitialized;
+
+// starts nethack
+function nethackStart(cb, inputModule = {}) {
+    if(typeof cb !== "string" && typeof cb !== "function") throw new TypeError("expected first argument to be 'Function' or 'String' representing global callback function name");
+    if(typeof inputModule !== "object") throw new TypeError("expected second argument to be object");
+
+    let cbName;
+    if(typeof cb === "function") {
+        cbName = cb.name;
+        if (cbName === "") cbName = "__anonymousNetHackCallback";
+        if (globalThis[cbName] === undefined) globalThis[cbName] = cb;
+        else if (globalThis[cbName] !== cb) throw new Error (`'globalThis["${cbName}"]' is not the same as specified callback`);
+    }
+
+    /* global globalThis */
+    userCallback = globalThis[cbName];
+    if(typeof userCallback !==  "function") throw new TypeError(`expected 'globalThis["${cbName}"]' to be a function`);
+    // if(userCallback.constructor.name !== "AsyncFunction") throw new TypeError(`expected 'globalThis["${cbName}"]' to be an async function`);
+
+    // Emscripten Module config
+    Module = inputModule;
+    savedOnRuntimeInitialized = Module.onRuntimeInitialized;
+    Module.onRuntimeInitialized = function (... args) {
+        // after the WASM is loaded, add the shim graphics callback function
+        Module.ccall(
+            "shim_graphics_set_callback", // C function name
+            null, // return type
+            ["string"], // arg types
+            [cbName], // arg values
+            {async: true} // options
+        );
+
+        // if the user had their own onRuntimeInitialized(), call it now
+        if (savedOnRuntimeInitialized) savedOnRuntimeInitialized(... args);
+    };
+
+    // load and run the module
+    var factory = require(path.join(__dirname, "../build/nethack.js"));
+    factory(Module);
+}
+
+// TODO: ES6 'import' style module
+module.exports = nethackStart;
+