start constifying and destaticifying middle-pgsql
Merge remote-tracking branch 'MapQuest/kk_multiback' into mla_multi_backend
Don't use `const osmid_t &`.

The `osmid_t` is (probably) an 8-byte value, and a reference is
(probably) also an 8-byte value on most modern machines, so it
doesn't save us anything and adds an extra dereference.
Removed statics from `output_gazetteer_t`.