Code review comment for lp:~mir-team/mir/add-more-event-getters

And summarizing from IRC discussion about the symbols of mircommon (but outside the scope of this MP)

It would probably best if we split the mircommon library into its public and private parts (perhaps mircommon and mircommonprivate)

Private meaning the symbols needed only by mir libraries - mircommon, mirserver, etc - (basically what's exposed through src/include/common)

Public meaning any symbols for external consumption - like the apis defined in this MP, essentially what is exposed through include/common