Bring Lua to 5.4.6. (#1214)

This essentially re-does the work of #875 on top of master.

This is what I did to check that Cosmo's Lua extensions still worked:

```
$ build/bootstrap/make MODE=aarch64 o/aarch64/third_party/lua/lua
$ ape o/aarch64/third_party/lua/lua
>: 10
10
>: 010
8
>: 0b10
2
>: string.byte("\e")
27
>: "Hello, %s" % {"world"}
Hello, world
>: "*" * 3
***
```

`luaL_traceback2` was used to show the stack trace with parameter
values; it's used in `LuaCallWithTrace`, which is used in Redbean to run
Lua code. You should be able to see the extended stack trace by running
something like this: `redbean -e "function a(b)c()end a(2)"` (with
"params" indicating the extended stack trace):

```
stack traceback:
 [string "function a(b)c()end a(2)"]:1: in function 'a', params: b = 2;
 [string "function a(b)c()end a(2)"]:1: in main chunk
```
@pkulchenko confirmed that I get the expected result with the updated
code.

This is what I did to check that Lua itself still worked:

```
$ cd third_party/lua/test/
$ ape ../../../o/aarch64/third_party/lua/lua all.lua
```

There's one test failure, in `files.lua`:

```
***** FILE 'files.lua'*****
testing i/o
../../../o/aarch64/third_party/lua/lua: files.lua:84: assertion failed!
stack traceback:
[C]: in function 'assert'
files.lua:84: in main chunk
(...tail calls...)
all.lua:195: in main chunk
[C]: in ?
.>>> closing state <<<
```

That isn't a result of these changes; the same test is failing in
master.

The failure is here:

```lua
if not _port then   -- invalid seek
  local status, msg, code = io.stdin:seek("set", 1000)
  assert(not status and type(msg) == "string" and type(code) == "number")
end
```

The test expects a seek to offset 1,000 on stdin to fail — but it
doesn't. `status` ends up being the new offset rather than `nil`.

If I comment out that one test, the remaining tests succeed.

third_party/lua/test/utf8.lua

@@ -97,9 +97,15 @@ do    -- error indication in utf8.len
     assert(not a and b == p)
   end
   check("abc\xE3def", 4)
-  check("汉字\x80", #("汉字") + 1)
   check("\xF4\x9F\xBF", 1)
   check("\xF4\x9F\xBF\xBF", 1)
+  -- spurious continuation bytes
+  check("汉字\x80", #("汉字") + 1)
+  check("\x80hello", 1)
+  check("hel\x80lo", 4)
+  check("汉字\xBF", #("汉字") + 1)
+  check("\xBFhello", 1)
+  check("hel\xBFlo", 4)
 end
 
 -- errors in utf8.codes
@@ -112,6 +118,16 @@ do
   end
   errorcodes("ab\xff")
   errorcodes("\u{110000}")
+  errorcodes("in\x80valid")
+  errorcodes("\xbfinvalid")
+  errorcodes("αλφ\xBFα")
+
+  -- calling interation function with invalid arguments
+  local f = utf8.codes("")
+  assert(f("", 2) == nil)
+  assert(f("", -1) == nil)
+  assert(f("", math.mininteger) == nil)
+
 end
 
 -- error in initial position for offset
@@ -214,7 +230,7 @@ do
   check(s, {0x10000, 0x1FFFFF}, true)
 end
 
-x = "日本語a-4\0éó"
+local x = "日本語a-4\0éó"
 check(x, {26085, 26412, 35486, 97, 45, 52, 0, 233, 243})