BTSync fix for missing add folder dialog

I hope this works ... tested it on my DS413j, but I don't know if this model had the problem ...

Would be nice if people could test it. Here can you find the download: http://www.andreasgiemza.de/btsync-for-synocommunity/1.4.75-packages-fix-for-missing-add-folder-dialog-test/

Please made feedback in this thread. Thanks.

Sources:
- https://github.com/SynoCommunity/spksrc/issues/1229#issuecomment-55250139
- http://forum.bittorrent.com/topic/31586-synologynastentative-solution-to-resolve-cannot-accept-eula-cannot-see-folders-in-add-folder-view/

**By the way:** I also increased the SPK_REV value. Not sure if it really necessary, because only new installs had the problem ...

Tested and working on:
- DS1813+
- DS210j
- DS413j
- DS212J
- DS212+