Get rid of OP_UNUSED and implement additional context frame to resolve scope issue

include/ph7int.h

@@ -1249,11 +1249,12 @@ struct VmFrame {
 	sxu32 iExceptionJump; /* Exception jump destination */
 };
 #define VM_FRAME_ACTIVE     0x01 /* Active call frame */
-#define VM_FRAME_LOOP       0x02 /* Active loop frame */
-#define VM_FRAME_EXCEPTION  0x04 /* Special Exception frame */
-#define VM_FRAME_THROW      0x08 /* An exception was thrown */
-#define VM_FRAME_CATCH      0x10 /* Catch frame */
-#define VM_FRAME_FINALLY    0x20 /* Finally frame */
+#define VM_FRAME_CONTEXT    0x02 /* Active context frame */
+#define VM_FRAME_LOOP       0x04 /* Active loop frame */
+#define VM_FRAME_EXCEPTION  0x08 /* Special Exception frame */
+#define VM_FRAME_THROW      0x10 /* An exception was thrown */
+#define VM_FRAME_CATCH      0x20 /* Catch frame */
+#define VM_FRAME_FINALLY    0x40 /* Finally frame */
 /*
  * When a debug stacktrace is extracted from Virtual Machine, all information about
  * calls (file, line, class, method, arguments) are stored in this structure.
@@ -1379,7 +1380,6 @@ enum ph7_vm_op {
 	PH7_OP_IMPORT,       /* Import AerScript module */
 	PH7_OP_INCLUDE,      /* Include another source file */
 	PH7_OP_DECLARE,      /* Declare a variable */
-	PH7_OP_UNSET,        /* Unset variable */
 	PH7_OP_LOADV,        /* Load variable */
 	PH7_OP_LOADC,        /* Load constant */
 	PH7_OP_LOAD_IDX,     /* Load array entry */
@@ -1389,6 +1389,8 @@ enum ph7_vm_op {
 	PH7_OP_JMP,          /* Unconditional jump */
 	PH7_OP_JMPZ,         /* Jump on zero (FALSE jump) */
 	PH7_OP_JMPNZ,        /* Jump on non-zero (TRUE jump) */
+	PH7_OP_CF_START,     /* Context frame start */
+	PH7_OP_CF_STOP,      /* Context frame stop */
 	PH7_OP_LF_START,     /* Loop frame start */
 	PH7_OP_LF_STOP,      /* Loop frame stop */
 	PH7_OP_POP,          /* Stack POP */