add tests for delete() on the hash table

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
fix a bug in get() for the hash table

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
polish the code a little

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
remove typedef statements for structures

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>