* gnu/packages/protobuf.scm (protobuf): Update to 2.6.1. [source]: Update to new upstream URL.
* gnu/packages/protobuf.scm (python-protobuf, python2-protobuf): New variables. Co-authored-by: Leo Famulari <leo@famulari.name>
* gnu/packages/protobuf.scm: New file. * gnu-system.am (GNU_SYSTEM_MODULES): Add it.