- 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.
For the tutorial the old Makefiles are saved as Makefile.simple in all
the respective directories.
Use generated config.h instead of command-line passing of preprocessor
flags.
Updated support files from current automake.
