Makefile.am: remove protobuf-c-rpc
configure.ac: remove protobuf-c-rpc
.travis.yml: remove protobuf-c-rpc
.gitignore: remove protobuf-c-rpc
protobuf-c-rpc/: remove
TODO: remove protobuf-c-rpc
README.md: update due to the protobuf-c-rpc split out