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/gc.lua

@@ -125,7 +125,7 @@ do
   end
 
   a:test()
-
+  _G.temp = nil
 end
 
 
@@ -134,7 +134,7 @@ do local f = function () end end
 
 
 print("functions with errors")
-prog = [[
+local prog = [[
 do
   a = 10;
   function foo(x,y)
@@ -153,22 +153,25 @@ do
     end
   end
 end
+rawset(_G, "a", nil)
+_G.x = nil
 
+do
 foo = nil
 print('long strings')
-x = "01234567890123456789012345678901234567890123456789012345678901234567890123456789"
+  local x = "01234567890123456789012345678901234567890123456789012345678901234567890123456789"
 assert(string.len(x)==80)
-s = ''
-k = math.min(300, (math.maxinteger // 80) // 2)
-for n = 1, k do s = s..x; j=tostring(n)  end
+  local s = ''
+  local k = math.min(300, (math.maxinteger // 80) // 2)
+  for n = 1, k do s = s..x; local j=tostring(n)  end
 assert(string.len(s) == k*80)
 s = string.sub(s, 1, 10000)
-s, i = string.gsub(s, '(%d%d%d%d)', '')
+  local s, i = string.gsub(s, '(%d%d%d%d)', '')
 assert(i==10000 // 4)
-s = nil
-x = nil
 
 assert(_G["while"] == 234)
+  _G["while"] = nil
+end
 
 
 --
@@ -227,8 +230,8 @@ end
 
 
 print("clearing tables")
-lim = 15
-a = {}
+local lim = 15
+local a = {}
 -- fill a with `collectable' indices
 for i=1,lim do a[{}] = i end
 b = {}
@@ -371,7 +374,7 @@ if T then
 
   warn("@on"); warn("@store")
   collectgarbage()
-  assert(string.find(_WARN, "error in __gc metamethod"))
+  assert(string.find(_WARN, "error in __gc"))
   assert(string.match(_WARN, "@(.-)@") == "expected"); _WARN = false
   for i = 8, 10 do assert(s[i]) end
 
@@ -552,6 +555,7 @@ do
     for i=1,1000 do _ENV.a = {} end   -- no collection during the loop
   until gcinfo() > 2 * x
   collectgarbage"restart"
+  _ENV.a = nil
 end
 
 
@@ -676,11 +680,13 @@ end
 -- just to make sure
 assert(collectgarbage'isrunning')
 
-do    -- check that the collector is reentrant in incremental mode
+do    -- check that the collector is not reentrant in incremental mode
+  local res = true
   setmetatable({}, {__gc = function ()
-    collectgarbage()
+    res = collectgarbage()
   end})
   collectgarbage()
+  assert(not res)
 end