CentOS: Fix build for old compiler version

src/libsync/discoveryphase.h

@@ -35,11 +35,12 @@ class Account;
  */
 
 struct SyncOptions {
+    SyncOptions() : _newBigFolderSizeLimit(-1), _confirmExternalStorage(false) {}
     /** Maximum size (in Bytes) a folder can have without asking for confirmation.
      * -1 means infinite */
-    qint64 _newBigFolderSizeLimit = -1;
+    qint64 _newBigFolderSizeLimit;
     /** If a confirmation should be asked for external storages */
-    bool _confirmExternalStorage = false;
+    bool _confirmExternalStorage;
 };