[Tests] Fix compilation of several fassign tests on clang

In order to reuse the same source file, the fassign tests pass in
the values to be assigned as a preprocessor define. Unfortunately,
the preprocessor of clang 3.3 dies on this list if it contains spaces.
fix duneproject to create working CMakeLists.txt
Merge remote-tracking branch 'origin/p/muething/fix-fassign-test'

fix FS#1301