BUG #15705: psql autocompletion is not always correct with latest libedit

The following bug has been logged on the website:

Bug reference:      15705
Logged by:          Alexander Pyhalov
Email address:      apyhalov@gmail.com
PostgreSQL version: 11.2
Operating system:   OpenIndiana
Description:

After updating libedit from 20170329-3.1 to 20181209-3.1 we see the
following issue in psql:
while typing "create user test encr<TAB>" I see:
> create  user test encrypted\ password 
(note \ before space)
The issue seems to be in
https://github.com/NetBSD/src/commit/47081400d868e1d6dd5629bea97c599c48404839
- now libedit treats input as file names and escapes it accordingly.