BUG/MEDIUM: backend: Update hash to use unsigned int throughout

When we were generating a hash, it was done using an unsigned long.  When the hash was used
to select a backend, it was sent as an unsigned int.  This made it difficult to predict which
backend would be selected.

This patch updates get_hash, and the hash methods to use an unsigned int, to remain consistent
throughout the codebase.

This fix should be backported to 1.5 and probably in part to 1.4.