load and execute all ~/.fgfs/Nasal/*.nas files in alphabetic order after

the $FG_ROOT/Nasal/*.nas ones are done. This allows to use props.Node etc.
immediately, without requirement for settimer(func{}, 0) constructions.

Rationale:
- clean separation of local additions (and hacks :-) from standard files
- users might not have write permission to $FG_ROOT/Nasal/ or shouldn't
  have to su to root for writing Nasal code

Nasal/globals.nas

@@ -110,3 +110,32 @@ printlog = func(level, args...) {
 }
 
 
+##
+# Load and execute ~/.fgfs/Nasal/*.nas files in alphabetic order
+# after all $FG_ROOT/Nasal/*.nas files were loaded.
+#
+_setlistener("/sim/signals/nasal-dir-initialized", func {
+    var path = getprop("/sim/fg-home") ~ "/Nasal";
+    if ((var dir = directory(path)) == nil) return;
+    foreach (var file; sort(dir, cmp)) {
+        if (substr(file, -4) != ".nas") continue;
+
+        var module = substr(file, 0, size(file) - 4);
+        file = path ~ "/" ~ file;
+        printlog("info", ">>> executing local Nasal file ", file);
+
+        if (!contains(globals, module)) var locals = globals[module] = {};
+        elsif (typeof(globals[module]) == "hash") var locals = globals[module];
+        else var locals = {};
+
+        var err = [];
+        var code = call(func { compile(io.readfile(file), file) }, nil, err);
+        if (size(err)) {
+            print(file ~ ": " ~ err[0]);
+            continue;
+        }
+        call(bind(code, globals), nil, nil, locals, err);
+        debug.printerror(err);
+    }
+});
+