Added cmake-unit.
Small documentation fixes.
Fix handling of multi-value options.

Don't pass variables to represent lists when we can use multi-value
options to do that and fix handling of the COMMENT option, which was
in the wrong section and never got parsed.
Add unit tests for cppcheck-target-cmake functionality.
Merge pull request #6 from smspillaz/cppcheck-target-cmake.item_6

Add tests for cppcheck-target-cmake