Before this change the tests ran in about 12m34 and afterwards in
about 6m20, although the real change is more dramatic if you only run
tests from the tests/ subdirectory (as language tests still run serially).
This breaks valgrinding for now, which I intend to fix properly later.
Create a new top-level directory called test-data, which will carry
all the test data which is large and/or shared between multiple tests.
There are actually several new subdirectories created:
test-data/binaries: The pre-built binary and library files for random
architectures that we use to test various architecture detection
features (was part of tests/data).
test-data/blank-disks: The blank disks which are used for disk format
detection (was part of tests/data).
test-data/files: Other miscellaneous test files from tests/data that
are not included in the above.
test-data/phony-guests: The phony guests (was tests/guests).
test-data: The top-level directory builds the 'test.iso' image file
that is used for testing the C API and in miscellaneous other tests.
Instead of hardcoding the location of perl (assuming it is installed in
/usr), use /usr/bin/env to run it, and thus picking it from $PATH.
This makes it possible to run these scripts also on installations with
perl in a different prefix than /usr.
Also, given that we want enable warnings on scripts, turn the -w
previously in shebang to explicit "use warnings;" in scripts which
didn't have it before.
