Silence warnings from ignored Result values

For a few of the locations where error handling is done correctly this
does the right thing.  For most other places it gracefully ignores any
issues which is what the original code did as well.  Errors are
already logged by the called functions in those cases.

src/dc_msg.rs

@@ -1110,13 +1110,15 @@ pub unsafe fn dc_delete_msg_from_db(context: &Context, msg_id: uint32_t) {
             &context.sql,
             "DELETE FROM msgs WHERE id=?;",
             params![(*msg).id as i32],
-        );
+        )
+        .ok();
         sql::execute(
             context,
             &context.sql,
             "DELETE FROM msgs_mdns WHERE msg_id=?;",
             params![(*msg).id as i32],
-        );
+        )
+        .ok();
     }
     dc_msg_unref(msg);
 }