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.
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.
Implement 'set-label' for XFS filesystems.
Fix the call for btrfs. Previous
commit d5817537fa added some bogus
documentation implying this call would work for btrfs, but it did
not.
Add tests.
