CMake source incompatible changes

[Alexander Neundorf]

Hi,

here: http://techbase.kde.org/Development/ECM_SourceIncompatChanges
I tried to document all cmake source-incompatible changes in our buildsystem 
between KDE4 and KF5 (except FindKDE4Internal.cmake itself, since this is not 
done yet).
Please try to keep that up-to-date and complete.
I think it's helpful for our developers.

Thanks
Alex