Mir's not building

[Daniel van Vugt]

Mir does not build on a fully updated wily system today. This is 
expected as the whole archive is "transitioning" (rebuilding) to GCC 5 
and a new C++ ABI.

A workaround for the time being is:
    cmake .. -DCMAKE_CXX_COMPILER=g++-4.9 -DCMAKE_C_COMPILER=gcc-4.9
or clang of course.

You can monitor the progress of the transition here:
    http://people.canonical.com/~ubuntu-archive/transitions/

Looks like we should be unblocked and over this problem by tomorrow.

- Daniel