D24467: Use ECMGenerateExportHeader to manage deprecated API better

[David Faure]

dfaure accepted this revision.

REPOSITORY
  R306 KParts

BRANCH
  deprecatedapi

REVISION DETAIL
  https://phabricator.kde.org/D24467

To: kossebau, #frameworks, dfaure, mlaurent
Cc: kde-frameworks-devel, LeGast00n, GB_2, michaelh, ngraham, bruns