Summary:
The code ifdefed by ENABLE_TRANSIENCY_CHECK does no longer compile and
has not compiled since the switch to Qt 5 and KF5 as it still uses
kDebug and (worse) kDBacktrace. There are several other changes which
broke the code and I failed trying to get it to compile again. It's a
classic example of bitrot happening to code which is never getting
compiled.

As this has not been in a state which could compile for at least several
years, I think it's best to completely remove it.

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D7958