patch 8.0.0371: leaking memory when setting v:completed_item

Problem:    Leaking memory when setting v:completed_item.
Solution:   Or the flags instead of setting them.

Author: brammool

src/eval.c

@@ -6640,7 +6640,7 @@ set_vim_var_dict(int idx, dict_T *val)
 	    if (HASHITEM_EMPTY(hi))
 		continue;
 	    --todo;
-	    HI2DI(hi)->di_flags = DI_FLAGS_RO | DI_FLAGS_FIX;
+	    HI2DI(hi)->di_flags |= DI_FLAGS_RO | DI_FLAGS_FIX;
 	}
     }
 }

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    371,
 /**/
     370,
 /**/