Remove pointer to deinit() routine from QCoreApplication at deinitialization

REVIEW: 115159
Fixed "unused variable" warning in qca-gcrypt plugin
cmake: use install(FILES ...) instead of old style install_files
cmake: use QT_HEADER_DIR instead of QT_INCLUDE_DIR

Qt/Mac frameworks has two include dirs.
One is the framework include for which CMake will add a -F flag
and the other is an include dir for non-framework Qt modules.
QT_INCLUDE_DIR contains both.
QT_HEADER_DIR is for non-framework Qt modules.