Qt: Unify coding style and encoding

* qt/main.cpp, qt/pinentryconfirm.cpp, qt/pinentryconfirm.h,
  qt/pinentrydialog.cpp, qt/pinentrydialog.h: Use KDE coding style.
  Encode as UTF-8.

Code reformatted using kde-dev-scripts/astyle-kdelibs.
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