Prep v228: Substitute declaration masks (1/4)

Prep v228: Substitute declaration masks (1/4)

Although it looks very ugly, substitute all declaration masks of the
form:

  // UNNEEDED type foo(...);

with:

  /// UNNEEDED by elogind
  #if 0
  type foo(...);
  #endif // 0

to make future merging of upstream pathes easier, as the relevant
lines themselves are not changed any more.