qt5base: fix examples compile without opengl support

qt5base: fix examples compile without opengl support

Fixes [1]:

  make[1]: Entering directory '.../build/qt5base-5.9.1/examples/opengl'
  cd hellowindow/ && ( test -e Makefile || .../build/qt5base-5.9.1/bin/qmake -o Makefile .../build/qt5base-5.9.1/examples/opengl/hellowindow/hellowindow.pro ) && make -f Makefile
  make[2]: Entering directory '.../build/qt5base-5.9.1/examples/opengl/hellowindow'
  .../host/bin/sparc-linux-g++ -c -pipe -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os --sysroot=.../host/sparc-buildroot-linux-uclibc/sysroot -O2 -O3 -fno-exceptions -Wall -W -D_REENTRANT -fPIC -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I. -I../../../include/QtGui/5.9.1 -I../../../include/QtGui/5.9.1/QtGui -I../../../include -I../../../include/QtGui -I../../../include/QtCore/5.9.1 -I../../../include/QtCore/5.9.1/QtCore -I../../../include/QtCore -I.moc -I../../../mkspecs/devices/linux-buildroot-g++ -o .obj/hellowindow.o hellowindow.cpp
  In file included from hellowindow.cpp:51:0:
  hellowindow.h:96:5: error: ‘QOpenGLShaderProgram’ does not name a type
       QOpenGLShaderProgram *m_program;
       ^~~~~~~~~~~~~~~~~~~~
  hellowindow.h:97:5: error: ‘QOpenGLBuffer’ does not name a type
       QOpenGLBuffer m_vbo;
       ^~~~~~~~~~~~~
  hellowindow.cpp: In constructor ‘Renderer::Renderer(const QSurfaceFormat&, Renderer*, QScreen*)’:
  hellowindow.cpp:62:40: error: invalid use of incomplete type ‘class QOpenGLContext’
       m_context = new QOpenGLContext(this);
                                          ^
  In file included from ../../../include/QtGui/qsurfaceformat.h:1:0,
                   from ../../../include/QtGui/../../src/gui/kernel/qsurface.h:45,
                   from ../../../include/QtGui/qsurface.h:1,
                   from ../../../include/QtGui/../../src/gui/kernel/qwindow.h:51,
                   from ../../../include/QtGui/qwindow.h:1,
                   from ../../../include/QtGui/QWindow:1,
                   from hellowindow.h:51,
                   from hellowindow.cpp:51:

[1] http://autobuild.buildroot.net/results/001/001bc930014fca8c2a8b7a390350b4e1a15fa375/build-end.log

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>