Add more missing libc/libc++ functions

- Add sched_rr_get_interval()
- Add `unbuffer` command example
- Add more locale function stubs
- Vendor most of remaining libcxx content

libc/calls/sched_rr_get_interval.c

@@ -0,0 +1,42 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/intrin/describeflags.internal.h"
+
+int sys_sched_rr_get_interval(int, struct timespec *) hidden;
+
+/**
+ * Returns round-robin `SCHED_RR` quantum for `pid`.
+ *
+ * @param pid is id of process (where 0 is same as getpid())
+ * @param tp receives output interval
+ * @return 0 on success, or -1 w/ errno
+ * @error ENOSYS if not Linux or FreeBSD
+ * @error EFAULT if `tp` memory is invalid
+ * @error EINVAL if invalid `pid`
+ * @error ESRCH if could not find `pid`
+ */
+int sched_rr_get_interval(int pid, struct timespec *tp) {
+  int rc;
+  rc = sys_sched_rr_get_interval(pid, tp);
+  STRACE("sched_rr_get_interval(%d, [%s]) → %d% m", pid,
+         DescribeTimespec(rc, tp), rc);
+  return rc;
+}