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/readlink.c

@@ -22,16 +22,10 @@
 /**
  * Reads symbolic link.
  *
- * This does *not* nul-terminate the buffer.
- *
- * It is recommended that malloc() be linked into your program when
- * using this function. Otherwise the buffer should be larger. It should
- * also be noted that, without malloc, long names with many astral plane
- * characters might not decode properly.
- *
  * @param path must be a symbolic link pathname
  * @param buf will receive symbolic link contents, and won't be modified
  *     unless the function succeeds (with the exception of no-malloc nt)
+ *     and this buffer will *not* be nul-terminated
  * @return number of bytes written to buf, or -1 w/ errno; if the
  *     return is equal to bufsiz then truncation may have occurred
  * @see readlinkat(AT_FDCWD, ...) for modern version of this