Code review comment for lp:~albaguirre/mir/fix-1465883

There *is* a protobuf issue preventing us from doing that; see for example the failures on input-methods-can-... when I bumped protobuf ABI (eg: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-runner-mako/5597/console )

The issue is that protobuf will abort() if it's loaded twice, and bumping mirprotobuf ABI ensures that it's loaded twice. Otherwise we wouldn't be building libmirprotobuf.so at all, and would be statically linking it as nature intended.