Fix build for unusual protobuf environments
Fix build for unusual protobuf environments

Use ```protoc``` executable and Protobuf include path found by Protobuf
cmake module instead of relying that they are located in standard places.

rTreutlein/atomspace,AmeBel/atomspace,AmeBel/atomspace,rTreutlein/atomspace,AmeBel/atomspace,AmeBel/atomspace,rTreutlein/atomspace,rTreutlein/atomspace,rTreutlein/atomspace,AmeBel/atomspace