Make more improvements

This change includes many bug fixes, for the NT polyfills, strings,
memory, boot, and math libraries which were discovered by adding more
tools for recreational programming, such as PC emulation. Lemon has also
been vendored because it works so well at parsing languages.

libc/calls/dup-nt.c

@@ -34,13 +34,13 @@ textwindows int dup$nt(int oldfd, int newfd, int flags) {
   if (newfd == -1) {
     if ((newfd = createfd()) == -1) return -1;
   } else if (isfdindex(newfd)) {
-    close(newfd);
-  } else if (isfdlegal(newfd)) {
+    if (g_fds.p[newfd].kind != kFdEmpty) {
+      close(newfd);
+    }
+  } else {
     do {
       if (growfds() == -1) return -1;
     } while (newfd >= g_fds.n);
-  } else {
-    return ebadf();
   }
   if (DuplicateHandle(GetCurrentProcess(), g_fds.p[oldfd].handle,
                       GetCurrentProcess(), &g_fds.p[newfd].handle, 0,