Implement retz and retnz instruction

Author: zzo38

class.doc

@@ -1917,6 +1917,14 @@ ret  ( -- )
   at the end of a code block.) For a user defined function call, or a
   subroutine call, these restrictions are not applicable.
 
+retnz  ( z -- ? )
+  If true, then works like ret (the value is kept); but if false, then the
+  value is discarded and then it continues from here instead.
+
+retz  ( z -- ? )
+  If false, then works like ret (the value is kept); but if true, then the
+  value is discarded and then it continues from here instead.
+
 rot  ( x y z -- y z x )
 
 -rot  ( x y z -- z x y )

exec.c

@@ -3251,6 +3251,8 @@ static void execute_program(Uint16*code,int ptr,Uint32 obj) {
     case OP_REPLACE: NoIgnore(); StackReq(5,1); t5=Pop(); t4=Pop(); t3=Pop(); t2=Pop(); t1=Pop(); Push(v_replace(obj,t1,t2,t3,t4,t5)); break;
     case OP_REPLACE_D: NoIgnore(); StackReq(5,0); t5=Pop(); t4=Pop(); t3=Pop(); t2=Pop(); t1=Pop(); v_replace(obj,t1,t2,t3,t4,t5); break;
     case OP_RET: return;
+    case OP_RETNZ: StackReq(1,1); t1=Pop(); if(v_bool(t1)) { Push(t1); return; } break;
+    case OP_RETZ: StackReq(1,1); t1=Pop(); if(!v_bool(t1)) { Push(t1); return; } break;
     case OP_ROT: StackReq(3,3); t3=Pop(); t2=Pop(); t1=Pop(); Push(t2); Push(t3); Push(t1); break;
     case OP_ROTBACK: StackReq(3,3); t3=Pop(); t2=Pop(); t1=Pop(); Push(t3); Push(t1); Push(t2); break;
     case OP_RSH: StackReq(2,1); t2=Pop(); Numeric(t2); t1=Pop(); Numeric(t1); Push(NVALUE(t2.u&~31?0:t1.u>>t2.u)); break;

instruc

@@ -91,6 +91,8 @@ over
 *goto
 *CallSub
 ret
+retnz
+retz
 -case
 -or
 -and