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/lobject.h

@@ -13,11 +13,14 @@
 #define LUA_TPROTO   (LUA_NUMTYPES + 1) /* function prototypes */
 #define LUA_TDEADKEY (LUA_NUMTYPES + 2) /* removed keys in tables */
 
+
+
 /*
 ** number of all possible types (including LUA_TNONE but excluding DEADKEY)
 */
 #define LUA_TOTALTYPES (LUA_TPROTO + 2)
 
+
 /*
 ** tags for Tagged Values have the following use of bits:
 ** bits 0-3: actual tag (a LUA_T* constant)
@@ -39,6 +42,8 @@ typedef union Value {
   lua_CFunction f; /* light C functions */
   lua_Integer i;   /* integer numbers */
   lua_Number n;    /* float numbers */
+  /* not used, but may avoid warnings for uninitialized value */
+  lu_byte ub;
 } Value;
 
 
@@ -55,7 +60,7 @@ typedef struct TValue {
 
 
 #define val_(o)		((o)->value_)
-#define valraw(o)	(&val_(o))
+#define valraw(o)	(val_(o))
 
 
 /* raw type tag of a TValue */
@@ -99,7 +104,7 @@ typedef struct TValue {
 #define settt_(o,t)	((o)->tt_=(t))
 
 
-/* main macro to copy values (from 'obj1' to 'obj2') */
+/* main macro to copy values (from 'obj2' to 'obj1') */
 #define setobj(L,obj1,obj2) \
 	{ TValue *io1=(obj1); const TValue *io2=(obj2); \
           io1->value_ = io2->value_; settt_(io1, io2->tt_); \
@@ -142,6 +147,17 @@ typedef union StackValue {
 /* index to stack elements */
 typedef StackValue *StkId;
 
+
+/*
+** When reallocating the stack, change all pointers to the stack into
+** proper offsets.
+*/
+typedef union {
+  StkId p;  /* actual pointer */
+  ptrdiff_t offset;  /* used while the stack is being reallocated */
+} StkIdRel;
+
+
 /* convert a 'StackValue' to a 'TValue' */
 #define s2v(o)	(&(o)->val)
 
@@ -602,8 +618,10 @@ typedef struct Proto {
 */
 typedef struct UpVal {
   CommonHeader;
-  lu_byte tbc;  /* true if it represents a to-be-closed variable */
-  TValue *v;  /* points to stack or to its own value */
+  union {
+    TValue *p;  /* points to stack or to its own value */
+    ptrdiff_t offset;  /* used while the stack is being reallocated */
+  } v;
   union {
     struct {  /* (when open) */
       struct UpVal *next;  /* linked list */
@@ -785,7 +803,7 @@ LUAI_FUNC void luaO_chunkid (char *out, const char *source, size_t srclen);
 ** Computes ceil(log2(x))
 */
 static inline int luaO_ceillog2 (unsigned int x) {
-  return --x ? bsr(x) + 1 : 0;
+  return --x ? _bsr(x) + 1 : 0;  // [jart]
 }
 
 #endif