Things left to do after killing Qt4 (obtained by grepping for Qt4 and 'Qt 4'):
* update INSTALL.cmake
* update INSTALL.MacOSX
* update cmake
* check whether development/autotests/keytest.py really needs QT4
  investigate references to Qt4 in keytest
* update or remove development/lyx.rpm.README
* update or remove development/lyxserver/server_monitor.cpp
* update or remove development/tools/count_total_lines_of_compiled_code.sh