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/sort.lua

@@ -20,7 +20,7 @@ end
 checkerror("wrong number of arguments", table.insert, {}, 2, 3, 4)
 
 local x,y,z,a,n
-a = {}; lim = _soft and 200 or 2000
+a = {}; local lim = _soft and 200 or 2000
 for i=1, lim do a[i]=i end
 assert(select(lim, unpack(a)) == lim and select('#', unpack(a)) == lim)
 x = unpack(a)
@@ -222,7 +222,7 @@ a = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
 table.sort(a)
 check(a)
 
-function perm (s, n)
+local function perm (s, n)
   n = n or #s
   if n == 1 then
     local t = {unpack(s)}
@@ -248,7 +248,7 @@ perm{1,2,3,3,5}
 perm{1,2,3,4,5,6}
 perm{2,2,3,3,5,6}
 
-function timesort (a, n, func, msg, pre)
+local function timesort (a, n, func, msg, pre)
   local x = os.clock()
   table.sort(a, func)
   x = (os.clock() - x) * 1000
@@ -257,7 +257,7 @@ function timesort (a, n, func, msg, pre)
   check(a, func)
 end
 
-limit = 50000
+local limit = 50000
 if _soft then limit = 5000 end
 
 a = {}
@@ -274,7 +274,7 @@ for i=1,limit do
   a[i] = math.random()
 end
 
-x = os.clock(); i=0
+local x = os.clock(); local i = 0
 table.sort(a, function(x,y) i=i+1; return y<x end)
 x = (os.clock() - x) * 1000
 print(string.format("Invert-sorting other %d elements in %.2f msec., with %i comparisons",
@@ -289,18 +289,19 @@ timesort(a, limit,  function(x,y) return nil end, "equal")
 
 for i,v in pairs(a) do assert(v == false) end
 
-A = {"álo", "\0first :-)", "alo", "then this one", "45", "and a new"}
-table.sort(A)
-check(A)
+AA = {"álo", "\0first :-)", "alo", "then this one", "45", "and a new"}
+table.sort(AA)
+check(AA)
 
-table.sort(A, function (x, y)
-          load(string.format("A[%q] = ''", x), "")()
+table.sort(AA, function (x, y)
+          load(string.format("AA[%q] = ''", x), "")()
           collectgarbage()
           return x<y
         end)
 
+_G.AA = nil
 
-tt = {__lt = function (a,b) return a.val < b.val end}
+local tt = {__lt = function (a,b) return a.val < b.val end}
 a = {}
 for i=1,10 do  a[i] = {val=math.random(100)}; setmetatable(a[i], tt); end
 table.sort(a)