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/runtime/mmap.c

@@ -27,6 +27,7 @@
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/kprintf.h"
+#include "libc/limits.h"
 #include "libc/log/backtrace.internal.h"
 #include "libc/log/libfatal.internal.h"
 #include "libc/log/log.h"
@@ -281,7 +282,7 @@ noasan void *mmap(void *addr, size_t size, int prot, int flags, int fd,
   } else if (__isfdkind(fd, kFdZip)) {
     STRACE("fd is zipos handle");
     res = VIP(einval());
-  } else if (__virtualmax &&
+  } else if (__virtualmax < LONG_MAX &&
              (__builtin_add_overflow((virtualused = GetMemtrackSize(&_mmi)),
                                      size, &virtualneed) ||
               virtualneed > __virtualmax)) {