I reverted the change and added `${CMAKE_SOURCE_DIR}/src` to protoc include dirs; Protoc now works ok, but g++ gives a strange compilcation error:

```
/home/adam/workspace/caffe/build/src/caffe/proto/caffe_pretty_print.pb.cc: In function ‘void caffe::protobuf_AddDesc_caffe_5fpretty_5fprint_2eproto()’:
/home/adam/workspace/caffe/build/src/caffe/proto/caffe_pretty_print.pb.cc:84:3: error: ‘protobuf_AddDesc_caffe_2fproto_2fcaffe_2eproto’ is not a member of ‘caffe’
   ::caffe::protobuf_AddDesc_caffe_2fproto_2fcaffe_2eproto();
   ^
```