Comment 7 for bug 619045

I've done a modification of the trunk version in the spice-up-cmake branch.
Now it is implemented in the following way:

- Unit testing is enabled by default for Debug builds and disabled for Release builds.
- For Debug builds WL_UNIT_TESTS can be set to OFF to disable testing. This removes the dependency to boost_unit_test_framework, but of course not the dependency to boost itself
- For Release builds, WL_UNIT_TESTS can be set to ON to enable automatic testing.
- You can also say "make test" if WL_UNIT_TESTS is enabled (by default or automatic)