patch 9.0.1031: Vim9 class is not implemented yet

Problem:    Vim9 class is not implemented yet.
Solution:   Add very basic class support.

src/vim9instr.c

@@ -113,6 +113,24 @@ generate_instr_debug(cctx_T *cctx)
     return isn;
 }
 
+/*
+ * Generate an ISN_CONSTRUCT instruction.
+ * The object will have "size" members.
+ */
+    int
+generate_CONSTRUCT(cctx_T *cctx, class_T *cl)
+{
+    isn_T	*isn;
+
+    RETURN_OK_IF_SKIP(cctx);
+    if ((isn = generate_instr(cctx, ISN_CONSTRUCT)) == NULL)
+	return FAIL;
+    isn->isn_arg.construct.construct_size = sizeof(object_T)
+			       + cl->class_obj_member_count * sizeof(typval_T);
+    isn->isn_arg.construct.construct_class = cl;
+    return OK;
+}
+
 /*
  * If type at "offset" isn't already VAR_STRING then generate ISN_2STRING.
  * But only for simple types.
@@ -163,6 +181,8 @@ may_generate_2STRING(int offset, int tolerant, cctx_T *cctx)
 	case VAR_JOB:
 	case VAR_CHANNEL:
 	case VAR_INSTR:
+	case VAR_CLASS:
+	case VAR_OBJECT:
 			 to_string_error(type->tt_type);
 			 return FAIL;
     }
@@ -2403,6 +2423,7 @@ delete_instr(isn_T *isn)
 	case ISN_COMPARESPECIAL:
 	case ISN_COMPARESTRING:
 	case ISN_CONCAT:
+	case ISN_CONSTRUCT:
 	case ISN_COND2BOOL:
 	case ISN_DEBUG:
 	case ISN_DEFER:
@@ -2457,6 +2478,7 @@ delete_instr(isn_T *isn)
 	case ISN_REDIRSTART:
 	case ISN_RETURN:
 	case ISN_RETURN_VOID:
+	case ISN_RETURN_OBJECT:
 	case ISN_SHUFFLE:
 	case ISN_SLICE:
 	case ISN_SOURCE: