The test system is Slackware 14.2, which uses Qt 4.8.7.
* WANT_WIN_QT4 is defined, and has the expected meaning. Qt 5 is still
the default.
* The QT_NO_SOUND macro now excludes all headers and declarations
relating to sound; the multimedia package is not needed to build
(on any Qt 4, 5 or 6).
* A new function, nh_qsprintf, replaces QString::asprintf, for Qt
older than 5.5. These versions do not have QString::asprintf.
* DYNAMIC_STATUSLINES is disabled for Qt older than 5.9. These versions
do not have QSplitter::replaceWidget.
