finally proper stack unwind in the evaluator

src/runtime/c/pgf/data.h

@@ -136,8 +136,9 @@ typedef enum {
   PGF_INSTR_PUSH        =  9,
   PGF_INSTR_EVAL        = 10,
   PGF_INSTR_DROP        = 13,
-  PGF_INSTR_FAIL        = 14,
-  PGF_INSTR_ADD         = 15
+  PGF_INSTR_JUMP        = 14,
+  PGF_INSTR_FAIL        = 15,
+  PGF_INSTR_ADD         = 16
 } PgfInstruction;
 
 typedef GuSeq PgfConcrs;