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/sock/inet_pton.c

@@ -19,9 +19,9 @@
 #include "libc/fmt/fmt.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
-#include "libc/sysv/errfuns.h"
 #include "libc/sysv/consts/af.h"
 #include "libc/sysv/consts/inaddr.h"
+#include "libc/sysv/errfuns.h"
 
 /**
  * Converts internet address string to binary.
@@ -32,16 +32,23 @@
  * @return 1 on success, 0 on src malformed, or -1 w/ errno
  */
 int inet_pton(int af, const char *src, void *dst) {
-  if (af == AF_INET) {
-    unsigned char *p = (unsigned char *)dst;
-    if (sscanf(src, "%hhu.%hhu.%hhu.%hhu", &p[0], &p[1], &p[2], &p[3]) == 4) {
-      return 1;
+  uint8_t *p;
+  int b, c, j;
+  if (af != AF_INET) return eafnosupport();
+  j = 0;
+  p = dst;
+  p[0] = 0;
+  while ((c = *src++)) {
+    if (isdigit(c)) {
+      b = c - '0' + p[j] * 10;
+      p[j] = MIN(255, b);
+      if (b > 255) return 0;
+    } else if (c == '.') {
+      if (++j == 4) return 0;
+      p[j] = 0;
     } else {
-      *(uint32_t *)dst = htonl(INADDR_TESTNET3);
       return 0;
     }
-  } else {
-    *(uint32_t *)dst = htonl(INADDR_TESTNET3);
-    return eafnosupport();
   }
+  return j == 3 ? 1 : 0;
 }