On HPUX, shl_load should be called with options BIND_IMMEDIATE rather

On HPUX, shl_load should be called with options BIND_IMMEDIATE rather
than BIND_DEFERRED.  That way, if the loaded library has unresolved
references, shl_load fails cleanly.  As we had it, shl_load would
succeed and then the dynlinker would call abort() when we try to call
into the loaded library.  abort()ing a backend is uncool.