QImage::constBits is qt >= 4.7 only
Partial compile fix
Merge branch 'master' of https://github.com/eile/DisplayCluster

Conflicts:
	src/core/PDF.cpp
Merge branch 'master' of https://github.com/BlueBrain/DisplayCluster

Conflicts:
	src/core/FpsCounter.cpp
RHEL compile fix
Unify with master
Merge pull request #73 from eile/master

Fix for RHEL6