Fix bugs and make improvements

- Get clone() working on FreeBSD
- Increase some Python build quotas
- Add more atomic builtins to chibicc
- Fix ASAN poisoning of alloca() memory
- Make MODE= mandatory link path tinier
- Improve the examples folder a little bit
- Start working on some more resource limits
- Make the linenoise auto-complete UI as good as GNU readline
- Update compile.com, avoiding AVX codegen on non-AVX systems
- Make sure empty path to syscalls like opendir raises ENOENT
- Correctly polyfill ENOENT vs. ENOTDIR on the New Technology
- Port bestline's paredit features to //third_party/linenoise
- Remove workarounds for RHEL 5.0 bugs that were fixed in 5.1

libc/calls/linkat-nt.c

@@ -30,7 +30,7 @@ textwindows int sys_linkat_nt(int olddirfd, const char *oldpath, int newdirfd,
     if (CreateHardLink(newpath16, oldpath16, NULL)) {
       return 0;
     } else {
-      return __winerr();
+      return __fix_enotdir3(__winerr(), newpath16, oldpath16);
     }
   } else {
     return -1;