Check memory

This is done using valgrind.

Run ```make check-memory``` to run tests under valgrind. Non C tests are skipped. Run ```make recheck-memory``` to rerun failed tests under valgrind.

Use ```-j8``` to parallelize valgrind checking, which makes things much faster.

Add some basic suppressions files. These can be expanded as we encounter more issues in underlying libraries.

No leak checking yet, that's dependent on the glib wip/gcleanup branch and not yet ready.