tests: Run valgrind also on binary tests.

tests: Run valgrind also on binary tests.

When configuring with --enable-valgrind we were only running valgrind
on tests with a shell wrapper script. This patch makes sure to also run
valgrind on "pure" binary tests. This found one small issue in libasm
where we could be writing some uninitialized padding to an ELF file.
And there were a couple tests that didn't clean up all the resources
they used. Both issues are also fixed with this patch.

Signed-off-by: Mark Wielaard <mark@klomp.org>