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/sysv/systemfive.S

@@ -374,7 +374,7 @@ _init_systemfive_stack:					# determinism ftw!
 	mov	%rsp,%rbp
 //	𝑠𝑙𝑖𝑑𝑒
 _init_systemfive_syscall:
-	mov	__NR_msyscall,%eax			# syscall origin protect
+/*	mov	__NR_msyscall,%eax			# syscall origin protect
 	cmp	$0xfff,%ax				# openbsd is pretty cool
 	jae	_init_systemfive_done
 	push	%rdi
@@ -385,7 +385,7 @@ _init_systemfive_syscall:
 	mov	$__privileged_size,%esi
 	syscall
 	pop	%rsi
-	pop	%rdi
+	pop	%rdi*/
 //	𝑠𝑙𝑖𝑑𝑒
 #endif /* TINY */
 _init_systemfive_done: