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.
The following tests were added during the 1.7 cycle to
demonstrate bugs:
alpha-similar operator operator-alpha self-copy-overlap
In all cases, the identical bug existed in the last major
release, (1.6.4), so these are not new regressions, but merely
bugs that we're now aware of. The correct way to handle bugs
such as these is to mark them as expected failures (XFAIL).
Application of a pure-alpha similar source is inconsistently handled
across the backends. The PDF/PS backends allow the rgb channels to bleed
through and the SVG backend mixes in pure white.
