BUG #14812: URI options cann't set with equal char.

The following bug has been logged on the website:

Bug reference: 14812
Logged by: Zhou Digoal
Email address: digoal(at)126(dot)com
PostgreSQL version: 10beta4
Operating system: CentOS 7.x x64
Description:

there is some confusion:

```
psql postgres://postgres(at)127(dot)0(dot)0(dot)1:1921/postgres?options="-c TimeZone =
+10"

psql: extra key/value separator "=" in URI query parameter: "options"
```

but in document:

https://www.postgresql.org/docs/10/static/libpq-connect.html

options
Specifies command-line options to send to the server at connection start.
For example, setting this to -c geqo=off sets the session's value of the
geqo parameter to off. Spaces within this string are considered to separate
command-line arguments, unless escaped with a backslash (\); write \\ to
represent a literal backslash. For a detailed discussion of the available
options, consult Chapter 19.