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/dup3-sysv.c

@@ -20,15 +20,13 @@
 #include "libc/calls/strace.internal.h"
 #include "libc/errno.h"
 
-#define __NR_dup3_linux 0x0124 /*RHEL5:CVE-2010-3301*/
-
 int32_t sys_dup3(int32_t oldfd, int32_t newfd, int flags) {
   static bool once, demodernize;
   int olderr, fd;
   if (!once) {
     olderr = errno;
     fd = __sys_dup3(oldfd, newfd, flags);
-    if ((fd == -1 && errno == ENOSYS) || fd == __NR_dup3_linux) {
+    if (fd == -1 && errno == ENOSYS) {
       STRACE("demodernizing %s() due to %s", "dup3", "RHEL5:CVE-2010-3301");
       demodernize = true;
       once = true;