Do quoting more carefully in replication commands

The security team received a report that pg_recvlogical was
careless about quoting --option arguments that are passed
into the START_REPLICATION command given to the server. In
principle this'd allow an attacker to inject unwanted stuff
into START_REPLICATION's options. However, we found it really
hard to envision a situation where somebody would be passing
strings obtained from untrustworthy sources to pg_recvlogical,
especially given that anything to do with replication already
requires pretty high privilege. So we're electing to treat this
as a garden-variety bug rather than one requiring the CVE process.

Looking around revealed other places also being sloppy about
quoting strings inserted into replication commands, but the same
who-would-do-that argument applies to them too. So here is a
patch that tries to clean all that up.

(I envision back-patching this all the way, but have not yet
looked at whether the back branches will require adjustments.)

regards, tom lane