-this is due to GCC bug 53431

fix warnings about double ;; in gdt

remove redundant line

- don't know exactly why it works like this, I suspect it is
due to the DEPENDENCYCHECK dune/xt/common/test/CMakeLists.txt
that depends on the xtcommon variable defined in the header
listing

- the DUNE_UNUSED macro is not a function, this lead to
some remaining warnings about unused variables

this closes #17

to avoid them gettin gheader-checked on their own

- adds ability to compare matrices (leftover from dune-stuff)
- top-level compare/test functions are (manually) generated from
a python script instead of C macros

or ctest execution. This broke filtering tests
with ctest -R MASK