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/sock.h

@@ -41,8 +41,8 @@ struct sockaddr_in {   /* Linux+NT ABI */
 };
 
 struct sockaddr_un {
-  uint16_t sun_family;  /* AF_UNIX */
-  char     sun_path[108];/* path */
+  uint16_t sun_family; /* AF_UNIX */
+  char sun_path[108];  /* path */
 };
 
 struct sockaddr_storage {
@@ -53,11 +53,15 @@ struct sockaddr_storage {
   };
 };
 
-struct ip_mreq  {
-  struct in_addr imr_multiaddr;   /* IP multicast address of group */
-  struct in_addr imr_interface;   /* local IP address of interface */
+struct ip_mreq {
+  struct in_addr imr_multiaddr; /* IP multicast address of group */
+  struct in_addr imr_interface; /* local IP address of interface */
 };
 
+struct linger {     /* Linux+XNU+BSD ABI */
+  int32_t l_onoff;  /* on/off */
+  int32_t l_linger; /* seconds */
+};
 
 struct pollfd {
   int32_t fd;