Fixed compilation problem on atlas with gcc.

AMDiS/CMakeLists.txt

AMDiS/src/AMDiS.h

AMDiS/src/ElementRegion_ED.cc

AMDiS/src/ElementRegion_ED.h

AMDiS/src/ProblemInstat.cc

AMDiS/src/ProblemStat.cc

AMDiS/src/SurfaceRegion_ED.cc

AMDiS/src/SurfaceRegion_ED.h

AMDiS/src/SystemVector.cc

AMDiS/src/SystemVector.h

AMDiS/src/io/DataCollector.h

AMDiS/src/io/DataCollector.hh

AMDiS/src/io/FileCompression.h

AMDiS/src/io/FileWriter.cc

AMDiS/src/io/FileWriter.h

AMDiS/src/io/FileWriter.hh

AMDiS/src/io/MacroWriter.cc

AMDiS/src/io/PngWriter.cc

AMDiS/src/io/PovrayWriter.cc

AMDiS/src/io/ValueWriter.cc