XRandR: Generic code cleanup
Summary:
No functional changes, white space added where sensible, debug messages now
without repetition of qCDebug(..) macros, modernized, keeps line limit.
Test Plan: Compiles and KScreen runs on X11.
Reviewers: KWin
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D23647