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/pipe2-sysv.c

@@ -19,16 +19,15 @@
 #include "libc/calls/internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
-
-#define __NR_pipe2_linux 0x0125 /*RHEL5:CVE-2010-3301*/
+#include "libc/sysv/consts/o.h"
+#include "libc/sysv/errfuns.h"
 
 int32_t sys_pipe2(int pipefd[hasatleast 2], unsigned flags) {
   int rc, olderr;
   if (!flags) goto OldSkool;
   olderr = errno;
   rc = __sys_pipe2(pipefd, flags);
-  if ((rc == -1 && errno == ENOSYS) ||
-      (SupportsLinux() && rc == __NR_pipe2_linux)) {
+  if (rc == -1 && errno == ENOSYS) {
     errno = olderr;
   OldSkool:
     if ((rc = sys_pipe(pipefd)) != -1) {