Doxygen will only process files with a @file documentation comment.
Up to now, none of our test code has such a comment, preventing the
cross-links to unit tests from working.
This is unfortunate, since unit tests, and even the code comments there,
can be considered as the most useful form of technical documentation.
Thus I'll start an initiative to fill in those missing comments automatically
the buildsystem will now pick up and link
all test cases according to the layer, e.g.
backend tests will automatically be linked
against the backend + library solely.
test.h introduces a PLANNED_TEST() macro for C code, shows what tests
are provided and so on (the nobug version did that since some time).
test names are now passed as identifers and translated to strings by the
macros.
A lot fixes for existing tests, replace some printfs with ECHO, cosmetics.
one threadpool (sync_many) test is broken and set to PLANNED, this needs
further testsuite support for dispatching output.
add a TEST nobug flag to test.h
