Use hidden symbol visibility for all plug-ins.
Use hidden symbol visibility for all plug-ins.

This ensures that plug-ins from external projects, which are build
by invoking this macro will use hidden visibility with gcc.

jcfr/CTK,danielknorr/CTK,fedorov/CTK,151706061/CTK,naucoin/CTK,Heather/CTK,pieper/CTK,jcfr/CTK,ddao/CTK,commontk/CTK,sankhesh/CTK,jcfr/CTK,Heather/CTK,CJGoch/CTK,151706061/CTK,danielknorr/CTK,mehrtash/CTK,sankhesh/CTK,ddao/CTK,SINTEFMedtek/CTK,Sardge/CTK,SINTEFMedtek/CTK,rkhlebnikov/CTK,Heather/CTK,jcfr/CTK,ddao/CTK,espakm/CTK,vovythevov/CTK,fedorov/CTK,mehrtash/CTK,mehrtash/CTK,laurennlam/CTK,lassoan/CTK,AndreasFetzer/CTK,SINTEFMedtek/CTK,Sardge/CTK,finetjul/CTK,AndreasFetzer/CTK,rkhlebnikov/CTK,sankhesh/CTK,vovythevov/CTK,CJGoch/CTK,danielknorr/CTK,lassoan/CTK,finetjul/CTK,AndreasFetzer/CTK,jcfr/CTK,laurennlam/CTK,espakm/CTK,CJGoch/CTK,pieper/CTK,naucoin/CTK,AndreasFetzer/CTK,commontk/CTK,SINTEFMedtek/CTK,pieper/CTK,pieper/CTK,finetjul/CTK,vovythevov/CTK,Heather/CTK,Sardge/CTK,CJGoch/CTK,vovythevov/CTK,espakm/CTK,finetjul/CTK,151706061/CTK,msmolens/CTK,commontk/CTK,msmolens/CTK,lassoan/CTK,mehrtash/CTK,Sardge/CTK,commontk/CTK,rkhlebnikov/CTK,rkhlebnikov/CTK,fedorov/CTK,laurennlam/CTK,fedorov/CTK,151706061/CTK,CJGoch/CTK,SINTEFMedtek/CTK,danielknorr/CTK,naucoin/CTK,espakm/CTK,151706061/CTK,msmolens/CTK,ddao/CTK,naucoin/CTK,laurennlam/CTK,msmolens/CTK,lassoan/CTK,sankhesh/CTK