feat: 适配 Lua 5.2.4 (lua_5.2.4 分支)

- lib/lua 替换为 Lua 5.2.4 官方源码; CMakeLists 补 lbitlib.c(5.2 linit 注册 bit32)、删 lutf8lib.c(5.2 无此文件)
- I/O 重定向机制改造: 5.2 无 lua_getextraspace → iopath 指针存入
  Registry 固定索引(IOPATH_REG_IDX=1), 回调经 get_iopath() 取回,
  free_lua 时释放 —— 该方案同样适用于更低版本
- typed interop 版本自适应: capture_result() 的 lua_isinteger 分支用
  #if LUA_VERSION_NUM >= 503 包裹, 5.2 及以下所有数字统一 CJT_NUM
- 测试跨版本适配: PackagePathConfig 接受 require 的两种返回语义;
  typed 数值断言 EXPECT_INT_OR_NUM 宏兼容有无 integer 子类型;
  大整数保真断言仅对 5.3+ 生效(5.2 经 double 必然丢精度)
- 验证: GTest 44/44 通过

lib/lua/lapi.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lapi.h $
+** $Id: lapi.h,v 2.7.1.1 2013/04/12 18:48:47 roberto Exp $
 ** Auxiliary functions from Lua API
 ** See Copyright Notice in lua.h
 */
@@ -11,42 +11,14 @@
 #include "llimits.h"
 #include "lstate.h"
 
+#define api_incr_top(L)   {L->top++; api_check(L, L->top <= L->ci->top, \
+				"stack overflow");}
 
-/* Increments 'L->top.p', checking for stack overflows */
-#define api_incr_top(L)	{L->top.p++; \
-			 api_check(L, L->top.p <= L->ci->top.p, \
-					"stack overflow");}
-
-
-/*
-** If a call returns too many multiple returns, the callee may not have
-** stack space to accommodate all results. In this case, this macro
-** increases its stack space ('L->ci->top.p').
-*/
 #define adjustresults(L,nres) \
-    { if ((nres) <= LUA_MULTRET && L->ci->top.p < L->top.p) \
-	L->ci->top.p = L->top.p; }
+    { if ((nres) == LUA_MULTRET && L->ci->top < L->top) L->ci->top = L->top; }
 
+#define api_checknelems(L,n)	api_check(L, (n) < (L->top - L->ci->func), \
+				  "not enough elements in the stack")
 
-/* Ensure the stack has at least 'n' elements */
-#define api_checknelems(L,n) \
-	api_check(L, (n) < (L->top.p - L->ci->func.p), \
-			  "not enough elements in the stack")
-
-
-/*
-** To reduce the overhead of returning from C functions, the presence of
-** to-be-closed variables in these functions is coded in the CallInfo's
-** field 'nresults', in a way that functions with no to-be-closed variables
-** with zero, one, or "all" wanted results have no overhead. Functions
-** with other number of wanted results, as well as functions with
-** variables to be closed, have an extra check.
-*/
-
-#define hastocloseCfunc(n)	((n) < LUA_MULTRET)
-
-/* Map [-1, inf) (range of 'nresults') into (-inf, -2] */
-#define codeNresults(n)		(-(n) - 3)
-#define decodeNresults(n)	(-(n) - 3)
 
 #endif