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/db.lua

@@ -16,7 +16,7 @@ end
 assert(not debug.gethook())
 
 local testline = 19         -- line where 'test' is defined
-function test (s, l, p)     -- this must be line 19
+local function test (s, l, p)     -- this must be line 19
   collectgarbage()   -- avoid gc during trace
   local function f (event, line)
     assert(event == 'line')
@@ -50,7 +50,7 @@ end
 
 
 -- test file and string names truncation
-a = "function f () end"
+local a = "function f () end"
 local function dostring (s, x) return load(s, x)() end
 dostring(a)
 assert(debug.getinfo(f).short_src == string.format('[string "%s"]', a))
@@ -72,7 +72,8 @@ dostring(a, string.format("=%s", string.rep('x', 500)))
 assert(string.find(debug.getinfo(f).short_src, "^x*$"))
 dostring(a, "=")
 assert(debug.getinfo(f).short_src == "")
-a = nil; f = nil;
+_G.a = nil; _G.f = nil;
+_G[string.rep("p", 400)] = nil
 
 
 repeat
@@ -120,6 +121,7 @@ else
 end
 ]], {2,3,4,7})
 
+
 test([[
 local function foo()
 end
@@ -128,6 +130,7 @@ A = 1
 A = 2
 A = 3
 ]], {2, 3, 2, 4, 5, 6})
+_G.A = nil
 
 
 test([[--
@@ -175,6 +178,8 @@ end
 
 test([[for i=1,4 do a=1 end]], {1,1,1,1})
 
+_G.a = nil
+
 
 do   -- testing line info/trace with large gaps in source
 
@@ -194,6 +199,50 @@ do   -- testing line info/trace with large gaps in source
     end
   end
 end
+_G.a = nil
+
+
+do   -- testing active lines
+  local function checkactivelines (f, lines)
+    local t = debug.getinfo(f, "SL")
+    for _, l in pairs(lines) do
+      l = l + t.linedefined
+      assert(t.activelines[l])
+      t.activelines[l] = undef
+    end
+    assert(next(t.activelines) == nil)   -- no extra lines
+  end
+
+  checkactivelines(function (...)   -- vararg function
+    -- 1st line is empty
+    -- 2nd line is empty
+    -- 3th line is empty
+    local a = 20
+    -- 5th line is empty
+    local b = 30
+    -- 7th line is empty
+  end, {4, 6, 8})
+
+  checkactivelines(function (a)
+    -- 1st line is empty
+    -- 2nd line is empty
+    local a = 20
+    local b = 30
+    -- 5th line is empty
+  end, {3, 4, 6})
+
+  checkactivelines(function (a, b, ...) end, {0})
+
+  checkactivelines(function (a, b)
+  end, {1})
+
+  for _, n in pairs{0, 1, 2, 10, 50, 100, 1000, 10000} do
+    checkactivelines(
+      load(string.format("%s return 1", string.rep("\n", n))),
+      {n + 1})
+  end
+
+end
 
 print'+'
 
@@ -244,7 +293,6 @@ foo(200, 3, 4)
 local a = {}
 for i = 1, (_soft and 100 or 1000) do a[i] = i end
 foo(table.unpack(a))
-a = nil
 
 
 
@@ -264,13 +312,14 @@ do   -- test hook presence in debug info
   debug.sethook()
   assert(count == 4)
 end
+_ENV.a = nil
 
 
 -- hook table has weak keys
 assert(getmetatable(debug.getregistry()._HOOKKEY).__mode == 'k')
 
 
-a = {}; L = nil
+a = {}; local L = nil
 local glob = 1
 local oldglob = glob
 debug.sethook(function (e,l)
@@ -311,7 +360,7 @@ function foo()
 end; foo()  -- set L
 -- check line counting inside strings and empty lines
 
-_ = 'alo\
+local _ = 'alo\
 alo' .. [[
 
 ]]
@@ -360,6 +409,7 @@ function g(a,b) return (a+1) + f() end
 
 assert(g(0,0) == 30)
  
+_G.f, _G.g = nil
 
 debug.sethook(nil);
 assert(not debug.gethook())
@@ -403,7 +453,7 @@ local function collectlocals (level)
 end
 
 
-X = nil
+local X = nil
 a = {}
 function a:f (a, b, ...) local arg = {...}; local c = 13 end
 debug.sethook(function (e)
@@ -426,6 +476,7 @@ a:f(1,2,3,4,5)
 assert(X.self == a and X.a == 1   and X.b == 2 and X.c == nil)
 assert(XX == 12)
 assert(not debug.gethook())
+_G.XX = nil
 
 
 -- testing access to local variables in return hook (bug in 5.2)
@@ -550,6 +601,7 @@ end
 
 debug.sethook()
 
+local g, g1
 
 -- tests for tail calls
 local function f (x)
@@ -595,7 +647,7 @@ h(false)
 debug.sethook()
 assert(b == 2)   -- two tail calls
 
-lim = _soft and 3000 or 30000
+local lim = _soft and 3000 or 30000
 local function foo (x)
   if x==0 then
     assert(debug.getinfo(2).what == "main")
@@ -844,7 +896,7 @@ do   -- testing debug info for finalizers
 
   -- create a piece of garbage with a finalizer
   setmetatable({}, {__gc = function ()
-    local t = debug.getinfo(2)   -- get callee information
+    local t = debug.getinfo(1)   -- get function information
     assert(t.namewhat == "metamethod")
     name = t.name
   end})
@@ -897,7 +949,7 @@ end
 
 
 print("testing debug functions on chunk without debug info")
-prog = [[-- program to be loaded without debug information (strip)
+local prog = [[-- program to be loaded without debug information (strip)
 local debug = require'debug'
 local a = 12  -- a local variable