Fix escaping in generated recovery.conf file.

In the primary_conninfo line that "pg_basebackup -R" generates, single
quotes in parameter values need to be escaped into \\'; the libpq parser
requires the quotes to be escaped into \', and recovery.conf parser requires
the \ to be escaped into \\.

Also, don't quote parameter values unnecessarily, to make the connection
string prettier. Most options in a libpq connection string don't need
quoting.

Reported by Hari Babu, closer analysis by Zoltan Boszormenyi, although I
didn't use his patch.