We were exposing the actual value of CAIRO_FORMAT_INVALID
through API functions already, so it makes sense to just
go ahead and put it in the cairo_format_t enum.
We frequently use '-' within the test name or format name and so we
encounter confusion as '-' is also used as the field separator. At times
this has caused a new test to break an old test because the new test would
match one of the old test's target specific reference images. So switch
everything over to use '.' between fields (test name, target, format,
subtest, etc.).
Avoid calling libtool to link every single test case, by building just one
binary from all the sources.
This binary is then given the task of choosing tests to run (based on user
selection and individual test requirement), forking each test into its own
process and accumulating the results.
