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

test/libc/calls/readansi_test.c

@@ -52,6 +52,7 @@ TEST(readansi, test) {
   EXPECT_STREQ("\xc2\x9bM", b);
   EXPECT_EQ(0, readansi(fds[0], b, sizeof(b)));
   EXPECT_STREQ("", b);
+  close(fds[0]);
   ASSERT_NE(-1, wait(&ws));
   ASSERT_TRUE(WIFEXITED(ws));
   ASSERT_EQ(0, WEXITSTATUS(ws));
@@ -73,6 +74,7 @@ TEST(readansi, testOperatingSystemCommand) {
   EXPECT_STREQ(s, b);
   EXPECT_EQ(0, readansi(fds[0], b, sizeof(b)));
   EXPECT_STREQ("", b);
+  close(fds[0]);
   ASSERT_NE(-1, wait(&ws));
   ASSERT_TRUE(WIFEXITED(ws));
   ASSERT_EQ(0, WEXITSTATUS(ws));