an internal compiler error with gcc4.0.0.
Repalced all occurences of "vec" by "this->vec" in eoGnuplot1DMonitor.cpp
so it is understood by the compiler :-(
- assume C++ standard-conforming environment
- add a user-option for gnuplot-support
- separate gnuplot-code into declaration and implementation,
so we can define at EO-build-time whether to use it or not.
Adopt code and Makefiles to above changes.
Some minor fixes.