Adjust pgbench to allow non-ASCII characters in variable names.
This puts it in sync with psql's notion of what is a valid variable name.
Like psql, we document that "non-Latin letters" are allowed, but actually
any non-ASCII character is accepted.
Fabien Coelho
Discussion: https://postgr.es/m/
20170405.094548.
1184280384967203518.t-ishii@sraoss.co.jp