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/ftruncate-nt.c

@@ -25,12 +25,10 @@ textwindows int sys_ftruncate_nt(int64_t handle, uint64_t length) {
   bool32 ok;
   int64_t tell;
   tell = -1;
-  if (SetFilePointerEx(handle, 0, &tell, kNtFileCurrent)) {
+  if ((ok = SetFilePointerEx(handle, 0, &tell, kNtFileCurrent))) {
     ok = SetFilePointerEx(handle, length, NULL, kNtFileBegin) &&
          SetEndOfFile(handle);
     SetFilePointerEx(handle, tell, NULL, kNtFileBegin);
-    return ok ? 0 : __winerr();
-  } else {
-    return __winerr();
   }
+  return ok ? 0 : __winerr();
 }