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/math.lua

@@ -50,7 +50,7 @@ end
 local msgf2i = "number.* has no integer representation"
 
 -- float equality
-function eq (a,b,limit)
+local function eq (a,b,limit)
   if not limit then
     if floatbits >= 50 then limit = 1E-11
     else limit = 1E-5
@@ -62,7 +62,7 @@ end
 
 
 -- equality with types
-function eqT (a,b)
+local function eqT (a,b)
   return a == b and math.type(a) == math.type(b)
 end
 
@@ -83,7 +83,7 @@ end
 do
   local x = -1
   local mz = 0/x   -- minus zero
-  t = {[0] = 10, 20, 30, 40, 50}
+  local t = {[0] = 10, 20, 30, 40, 50}
   assert(t[mz] == t[0] and t[-0] == t[0])
 end
 
@@ -849,6 +849,7 @@ do
   math.randomseed(x, y)    -- again should repeat the state
   assert(math.random(0) == res)
   -- keep the random seed for following tests
+  print(string.format("random seeds: %d, %d", x, y))
 end
 
 do   -- test random for floats