do not strip binary for packaging by default; improved name of disk image
Fix build on FreeBSD.

Notified by Raphael Kubo da Costa.
Update autotools for building with Qt5.

The option --enable-qt5 allows configuring for Qt5. The default is Qt4.
Nothing special is done with respect to Qt4, apart from pulling in the
correct libraries. Indeed, other than the core and gui libraries, now
also the concurrent and widgets libraries are needed.
avoid qt4 variable names
avoid qt4 variable names in cmake build