libpq: Improve error message when parsing URI parameters and keywords
The error message showing up when parameters or keywords include too
many whitespaces was "trailing data found", which was confusing because
there was no hint about what was actually wrong.
Issue introduced in
430ce189fc45, hence there is no need for a
backpatch.
Author: Yushi Ogiwara
Reviewed-by: Fujii Masao, Tom Lane, Bruce Momjian
Discussion: https://postgr.es/m/
645bd22a53c4da8a1bc7e1e52d9d3b52@oss.nttdata.com