Split gui/qt4/GLViewer.cpp.

gui/qt4/GLViewer.cpp is splitted on gui/qt4/GLViewer.cpp,
gui/qt4/GLViewerDisplay.cpp and gui/qt4/GLViewerMouse.cpp
to reduce the RAM-consumption during compilation.

It seems, gcc-4.8 requires too much RAM for Yade-compilation.
On some files it takes more than 3Gb, that is why there are
"memory exhaust" on 32-bit machines.
Remove pkg/dem/DomainLimiter.*

It seems, the code is unmaintained and requires too much
RAM for compilation.

Feel free to recover it, if it is necessary.