Use ECMGenerateExportHeader to manage deprecated API better

Summary:
Allows

• projects linking to KWayland to hide deprecated API up to a given version or silence deprecation warnings after a given version, using
  • -DKWAYLAND_DISABLE_DEPRECATED_BEFORE_AND_AT
  • -DKWAYLAND_NO_DEPRECATED
  • -DKWAYLAND_DEPRECATED_WARNINGS_SINCE
  • -DKWAYLAND_NO_DEPRECATED_WARNINGS
    
    or
  • -DKF_DISABLE_DEPRECATED_BEFORE_AND_AT
  • -DKF_NO_DEPRECATED
  • -DKF_DEPRECATED_WARNINGS_SINCE
  • -DKF_NO_DEPRECATED_WARNINGS

No support for "EXCLUDE_DEPRECATED_BEFORE_AND_AT", needs to be done by
someone with detailed knowledge about disabling implementation, if wanted.

Reviewers: KWin

Subscribers: zzag, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D24663