Fix memleak on Pixmap cache

as we load dives and dives, new DiveEvents will be created
but the transparent pixmap never deleted, also this makes
the transparent pixmap only for the correct event, not for
all of them.

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Make sure we always have copies of equipment descriptions

Having pointers copied around that might get freed elsewhere could be a
problem.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>