Add /statusz page to redbean plus other enhancements

redbean improvements:

- Explicitly disable corking
- Simulate Python regex API for Lua
- Send warmup requests in main process on startup
- Add Class-A granular IPv4 network classification
- Add /statusz page so you can monitor your redbean's health
- Fix regressions on OpenBSD/NetBSD caused by recent changes
- Plug Authorization header into Lua GetUser and GetPass APIs
- Recognize X-Forwarded-{For,Host} from local reverse proxies
- Add many additional functions to redbean Lua server page API
- Report resource usage of child processes on `/` listing page
- Introduce `-a` flag for logging child process resource usage
- Introduce `-t MILLIS` flag and `ProgramTimeout(ms)` init API
- Introduce `-H "Header: value"` flag and `ProgramHeader(k,v)` API

Cosmopolitan Libc improvements:

- Make strerror() simpler
- Make inet_pton() not depend on sscanf()
- Fix OpenExecutable() which broke .data section earlier
- Fix stdio in cases where it overflows kernel tty buffer
- Fix bugs in crash reporting w/o .com.dbg binary present
- Add polyfills for SO_LINGER, SO_RCVTIMEO, and SO_SNDTIMEO
- Polyfill TCP_CORK on BSD and XNU using TCP_NOPUSH magnums

New netcat clone in examples/nc.c:

While testing some of the failure conditions for redbean, I noticed that
BusyBox's `nc` command is pretty busted, if you use it as an interactive
tool, rather than having it be part of a pipeline. Unfortunately this'll
only work on UNIX since Windows doesn't let us poll on stdio and sockets
at the same time because I don't think they want tools like this running
on their platform. So if you want forbidden fruit, it's here so enjoy it

libc/stdio/fwrite.c

@@ -28,6 +28,30 @@
 #include "libc/str/str.h"
 #include "libc/sysv/consts/o.h"
 
+static ssize_t WritevAll(int fd, struct iovec *iov, int iovlen) {
+  ssize_t rc;
+  size_t wrote;
+  do {
+    if ((rc = writev(fd, iov, iovlen)) != -1) {
+      wrote = rc;
+      do {
+        if (wrote >= iov->iov_len) {
+          wrote -= iov->iov_len;
+          ++iov;
+          --iovlen;
+        } else {
+          iov->iov_base = (char *)iov->iov_base + wrote;
+          iov->iov_len -= wrote;
+          wrote = 0;
+        }
+      } while (wrote);
+    } else if (errno != EINTR) {
+      return -1;
+    }
+  } while (iovlen);
+  return 0;
+}
+
 /**
  * Writes data to stream.
  *
@@ -78,12 +102,10 @@ size_t fwrite(const void *data, size_t stride, size_t count, FILE *f) {
   iov[1].iov_base = data;
   iov[1].iov_len = n;
   n += f->beg;
-  if ((rc = writev(f->fd, iov, 2)) == -1) {
+  if (WritevAll(f->fd, iov, 2) == -1) {
     f->state = errno;
     return 0;
   }
-  m = rc;
-  if (n != m) abort();
   f->beg = 0;
   return count;
 }