get rid of LUAI_EXTRASPACE

Lua's power may come from extensibility, but the indirections are
currently in the way

src/lstate.c

@@ -24,9 +24,9 @@
 #include "ltm.h"
 
 
-#define state_size(x)	(sizeof(x) + LUAI_EXTRASPACE)
-#define fromstate(l)	(cast(lu_byte *, (l)) - LUAI_EXTRASPACE)
-#define tostate(l)   (cast(lua_State *, cast(lu_byte *, l) + LUAI_EXTRASPACE))
+#define state_size(x)	(sizeof(x))
+#define fromstate(l)	(cast(lu_byte *, (l)))
+#define tostate(l)   (cast(lua_State *, cast(lu_byte *, l)))
 
 
 /*

src/luaconf.h

@@ -664,15 +664,6 @@ union luai_Cast { double l_d; long l_l; };
 #endif
 
 
-/*
-@@ LUAI_EXTRASPACE allows you to add user-specific data in a lua_State
-@* (the data goes just *before* the lua_State pointer).
-** CHANGE (define) this if you really need that. This value must be
-** a multiple of the maximum alignment required for your machine.
-*/
-#define LUAI_EXTRASPACE		0
-
-
 /*
 @@ luai_userstate* allow user-specific actions on threads.
 ** CHANGE them if you defined LUAI_EXTRASPACE and need to do something

src/notes

@@ -0,0 +1,14 @@
+// Main thread combines a thread state and the global state
+typedef struct LG {
+  lua_State l;
+  global_State g;
+} LG;
+
+lua_State:
+  &{Value; int tt} stack, stack_last, base, top
+
+== todo stack
+delete statesize/from_state/to_state
+eradicate LUAI_EXTRASPACE
+lua_newstate
+lua_State's stack