Unlogged sequences

Preparatory test cleanup

Allow an alias to be attached to a JOIN ... USING

Add p_names field to ParseNamespaceItem

Make allow_system_table_mods settable at run time

Add a regression test for allow_system_table_mods

Remove any-user DML capability from allow_system_table_mods

pg_checksums: Handle read and write returns correctly

Better error messages for short reads/writes in SLRU

Use consistent style for checking return from system calls

Use explicit_bzero

Run UTF8-requiring collation tests by default