Code review comment for lp:~cjwatson/mir/stdint-include

I was just matching the existing uses in
src/server/report/lttng/scene_report_tp.h and
src/client/lttng/input_receiver_report_tp.h (and indeed various other
files). If you think I should change *all* the existing uses, then I
can add a revision to this branch that does that; but I'd rather not
make it inconsistent.