Solve current incompatibility between WITH_QGLVIEWER and WITH_QT5

[phcerdan]

QGLViewer can be based on qt5 (libQGLViewer-qt5).
QtGui/qapplication.h header in qt4 has moved to QtWidgets in qt5.
Solved that with preprocessor directives based on WITH_QT5 in some viewer examples.

[kerautret]

thanks @phcerdan for this PR. :) In fact from the edit of @naubry c548016 , this inclusion is already included in the DGtal/io/viewers/Viewer3D.h.
But you are right it was forgotten, so you just need to remove " the #include <QtGui/qapplication.h>" from the original code ...

[kerautret]

here as commented you can remove line " #include <QtGui/qapplication.h>" and the ifdef

[phcerdan]

Oh nice. Done

[dcoeurjo]

Thanks a lot @phcerdan for your 1st DGtal pull-request ;) (and @kerautret of course).

@phcerdan could you please add a changelog entry (bug fixes, IO package) before I merge ?

[naubry]

Thanks for this report. Indeed, I forgot these includes in my previous PR.

[phcerdan]

Thanks @dcoeurjo, quite happy to contribute a little! Changed log and squashed the 3 commits into one.

[dcoeurjo]

Great. Congrats @phcerdan for your first PR.