patch 9.0.1358: compilation error with some compilers

Problem:    Compilation error with some compilers.
Solution:   Avoid using "class" as member name.
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 90594ef..bc4a1fc 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -4071,7 +4071,7 @@
 			break;
 		    case ISN_PUSHCLASS:
 			tv->v_type = VAR_CLASS;
-			tv->vval.v_class = iptr->isn_arg.class;
+			tv->vval.v_class = iptr->isn_arg.classarg;
 			break;
 		    default:
 			tv->v_type = VAR_STRING;
@@ -6676,8 +6676,8 @@
 		break;
 	    case ISN_PUSHCLASS:
 		smsg("%s%4d PUSHCLASS %s", pfx, current,
-			iptr->isn_arg.class == NULL ? "null"
-				    : (char *)iptr->isn_arg.class->class_name);
+			iptr->isn_arg.classarg == NULL ? "null"
+				 : (char *)iptr->isn_arg.classarg->class_name);
 		break;
 	    case ISN_PUSHEXC:
 		smsg("%s%4d PUSH v:exception", pfx, current);