Fix bug in calculations of hash join buckets.

Fix bug in calculations of hash join buckets.

Commit 8cce08f168481c5fc5be4e7e29b968e314f1b41e used a left-shift
on a literal of 1 that could (in large allocations) be shifted by
31 or more bits.  This was assigned to a local variable that was
already declared to be a long to protect against overruns of int,
but the literal in this shift needs to be declared long to allow it
to work correctly in some compilers.

Backpatch to 9.5, where the bug was introduced.

Report and patch by KaiGai Kohei, slighly modified based on
discussion.