Changed internal representation of booleans

Instead of an explicit value (field 'b'), true and false use different
tag variants. This avoids reading an extra field and results in more
direct code. (Most code that uses booleans needs to distinguish between
true and false anyway.)

lopcodes.h

@@ -202,7 +202,8 @@ OP_LOADI,/*	A sBx	R[A] := sBx					*/
 OP_LOADF,/*	A sBx	R[A] := (lua_Number)sBx				*/
 OP_LOADK,/*	A Bx	R[A] := K[Bx]					*/
 OP_LOADKX,/*	A 	R[A] := K[extra arg]				*/
-OP_LOADBOOL,/*	A B C	R[A] := (Bool)B; if (C) pc++			*/
+OP_LOADFALSE,/*	A B	R[A] := false; if (B) pc++			*/
+OP_LOADTRUE,/*	A	R[A] := true					*/
 OP_LOADNIL,/*	A B	R[A], R[A+1], ..., R[A+B] := nil		*/
 OP_GETUPVAL,/*	A B	R[A] := UpValue[B]				*/
 OP_SETUPVAL,/*	A B	UpValue[B] := R[A]				*/