new metatable syntax for Lua: VM patch

mt.patch

diff --git a/src/Makefile b/src/Makefile
index e4a3cd6..9a29e1e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -8,7 +8,7 @@
 PLAT= none
 
 CC= gcc
-CFLAGS= -O2 -Wall $(MYCFLAGS)
+CFLAGS= -O2 -Wall $(MYCFLAGS) -DMT_PATCH
 AR= ar rcu
 RANLIB= ranlib
 RM= rm -f
diff --git a/src/lbaselib.c b/src/lbaselib.c
index 2a4c079..73b9a97 100644
--- a/src/lbaselib.c
+++ b/src/lbaselib.c
@@ -642,6 +642,11 @@ static void base_open (lua_State *L) {
   lua_setfield(L, -2, "__mode");  /* metatable(w).__mode = "kv" */
   lua_pushcclosure(L, luaB_newproxy, 1);
   lua_setglobal(L, "newproxy");  /* set global `newproxy' */
+  /* alternate metatable syntax */
+#ifdef MT_PATCH
+  lua_pushboolean(L, 1);
+  lua_setglobal(L, "_MT");
+#endif
 }
 
 
diff --git a/src/lvm.c b/src/lvm.c
index ee3256a..273a682 100644
--- a/src/lvm.c
+++ b/src/lvm.c
@@ -112,6 +112,15 @@ void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
     if (ttistable(t)) {  /* `t' is a table? */
       Table *h = hvalue(t);
       const TValue *res = luaH_get(h, key); /* do a primitive get */
+#ifdef MT_PATCH
+      if ( h->metatable && ttisstring(key) ) {
+        const char* key_str = getstr(tsvalue(key));
+        if ( strcmp(key_str, "__mt") == 0 ) {
+          sethvalue(L, val, h->metatable);
+          return;
+        }
+      }
+#endif
       if (!ttisnil(res) ||  /* result is no nil? */
           (tm = fasttm(L, h->metatable, TM_INDEX)) == NULL) { /* or no TM? */
         setobj2s(L, val, res);
@@ -138,6 +147,15 @@ void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
     if (ttistable(t)) {  /* `t' is a table? */
       Table *h = hvalue(t);
       TValue *oldval = luaH_set(L, h, key); /* do a primitive set */
+#ifdef MT_PATCH
+      if ( ttisstring(key) ) {
+        const char* key_str = getstr(tsvalue(key));
+        if ( strcmp(key_str, "__mt") == 0 ) {
+          h->metatable = (Table*) thvalue(val);
+          return;
+        }
+      }
+#endif
       if (!ttisnil(oldval) ||  /* result is no nil? */
           (tm = fasttm(L, h->metatable, TM_NEWINDEX)) == NULL) { /* or no TM? */
         setobj2t(L, oldval, val);