In addition to the actual removal of the softkeys API in QAction,
this commit removes some enums related to the softkeys feature:
  Qt::WA_MergeSoftkeys
  Qt::WA_MergeSoftkeysRecursively

It also removes some "zombie" enums:
  Qt::WindowSoftkeysVisibleHint = 0x40000000,
  Qt::WindowSoftkeysRespondHint = 0x80000000,

  (The only implementation that used these were removed when
  qapplication_s60.cpp and qwidget_s60.cpp were removed.)

Change-Id: Ib6fc6d543def4757383d5f19256199d9d190c614
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Janne Anttila <janne.anttila@digia.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>