Make improvements

- Get threads working on NetBSD
- Get threads working on OpenBSD
- Fix Emacs config for Emacs v28
- Improve --strace logging of sigset_t
- Improve --strace logging of struct stat
- Improve memory safety of DescribeThing functions
- Refactor auto stack allocation into LIBC_RUNTIME
- Introduce shell.com example which works on Windows
- Refactor __strace_thing into DescribeThing functions
- Document the CHECK macros and improve them in NDEBUG mode
- Rewrite MAP_STACK so it uses FreeBSD behavior across platforms
- Deprecate and discourage the use of MAP_GROWSDOWN (it's weird)

libc/log/thunks/__check_fail_eq.S

@@ -21,6 +21,10 @@
 
 //	Code-size saving thunk for CHECK_EQ() in NDEBUG mode.
 __check_fail_eq:
-	loadstr	"==",dx
+	lea	.Lop(%rip),%r8
 	jmp	__check_fail_ndebug
 	.endfn	__check_fail_eq,globl
+
+	.rodata.str1.1
+.Lop:	.asciz	"=="
+	.previous

libc/log/thunks/__check_fail_ge.S

@@ -21,6 +21,10 @@
 
 //	Code-size saving thunk for CHECK_GE() in NDEBUG mode.
 __check_fail_ge:
-	loadstr	">=",dx
+	lea	.Lop(%rip),%r8
 	jmp	__check_fail_ndebug
 	.endfn	__check_fail_ge,globl
+
+	.rodata.str1.1
+.Lop:	.asciz	">="
+	.previous

libc/log/thunks/__check_fail_gt.S

@@ -21,6 +21,10 @@
 
 //	Code-size saving thunk for CHECK_GT() in NDEBUG mode.
 __check_fail_gt:
-	loadstr	">",dx
+	lea	.Lop(%rip),%r8
 	jmp	__check_fail_ndebug
 	.endfn	__check_fail_gt,globl
+
+	.rodata.str1.1
+.Lop:	.asciz	">"
+	.previous

libc/log/thunks/__check_fail_le.S

@@ -21,6 +21,10 @@
 
 //	Code-size saving thunk for CHECK_LE() in NDEBUG mode.
 __check_fail_le:
-	loadstr	"<=",dx
+	lea	.Lop(%rip),%r8
 	jmp	__check_fail_ndebug
 	.endfn	__check_fail_le,globl
+
+	.rodata.str1.1
+.Lop:	.asciz	"<="
+	.previous

libc/log/thunks/__check_fail_lt.S

@@ -21,6 +21,10 @@
 
 //	Code-size saving thunk for CHECK_LT() in NDEBUG mode.
 __check_fail_lt:
-	loadstr	"<",dx
+	lea	.Lop(%rip),%r8
 	jmp	__check_fail_ndebug
 	.endfn	__check_fail_lt,globl
+
+	.rodata.str1.1
+.Lop:	.asciz	"<"
+	.previous

libc/log/thunks/__check_fail_ndebug.S

@@ -1,27 +0,0 @@
-/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
-│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2020 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/macros.internal.h"
-
-__check_fail_ndebug:
-	push	%rbp
-	mov	%rsp,%rbp
-	call	___check_fail_ndebug
-	pop	%rbp
-	jmp	__die				# fewer elements in backtrace
-	.endfn	__check_fail_ndebug,globl

libc/log/thunks/__check_fail_ne.S

@@ -21,6 +21,10 @@
 
 //	Code-size saving thunk for CHECK_NE() in NDEBUG mode.
 __check_fail_ne:
-	loadstr	"!=",dx
+	lea	.Lop(%rip),%r8
 	jmp	__check_fail_ndebug
 	.endfn	__check_fail_ne,globl
+
+	.rodata.str1.1
+.Lop:	.asciz	"!="
+	.previous