OP_NEWTABLE keeps exact size of arrays

OP_NEWTABLE is followed by an OP_EXTRAARG, so that it can keep
the exact size of the array part of the table to be created.
(Functions 'luaO_int2fb'/'luaO_fb2int' were removed.)

lopcodes.h

@@ -324,7 +324,8 @@ OP_EXTRAARG/*	Ax	extra (larger) argument for previous opcode	*/
   (*) In OP_SETLIST, if (B == 0) then real B = 'top'; if (C == 0) then
   next 'instruction' is EXTRAARG(real C).
 
-  (*) In OP_LOADKX, the next 'instruction' is always EXTRAARG.
+  (*) In OP_LOADKX and OP_NEWTABLE, the next 'instruction' is always
+  EXTRAARG.
 
   (*) For comparisons, k specifies what condition the test should accept
   (true or false).
@@ -375,4 +376,11 @@ LUAI_DDEC(const lu_byte luaP_opmodes[NUM_OPCODES];)
 #define LFIELDS_PER_FLUSH	50
 
 
+/*
+** In OP_NEWTABLE, array sizes smaller than LIMTABSZ are represented
+** directly in R(B). Otherwise, array size is given by
+**        (R(B) - LIMTABSZ) + EXTRAARG * LFIELDS_PER_FLUSH
+*/
+#define LIMTABSZ	(MAXARG_B - LFIELDS_PER_FLUSH)
+
 #endif