* Rename prepare_sources.py to configure.py; the operation is similar to
autoconf ./configure so the association is useful.
* Rename make_dist.py to dist.py.
* Generate only one source set (combined or separate) for one run of
configure.py.
* Change dist.py to run configure.py three times to generate the default
source sets.
* Use an autodeleted temporary directory for preparing sources, which
removes some of the manual temporary file handling.
* Fix temporary directory prefix.
* Add test run for Google V8 benchmark; while it's pointless for performance
measurement when the test runs in the cloud, it still provides a useful
regression harness.
* Add qecmatest and apitest assert and valgrind variants.
* Add valgrind massif test jobs to get approximate peak memory usage for a
'Hello world' test (involving startup RAM usage + minimal compilation
memory usage).
* Add Minisphere and DukLuv as initial examples of third party builds as
regression tests.
* Fix apitest executor, other minor fixes.