new `jobid' loadable builtin like ash-based shells; fix for nofork command substitution when followed by an asynchronous subshell using GNU nohup; fix for nofork command substitution to move the file descriptor moved to the anonymous file out of the user-accessible range

examples/scripts/nohup.sh

@@ -0,0 +1,12 @@
+(
+	if [ -t 1 ]; then
+		exec 1>>nohup.out || exec 1>>~/nohup.out
+	fi
+	if [ -t 2 ]; then
+		exec 2>&1
+	fi
+
+	trap '' SIGHUP
+
+	exec "$@"
+)