Changes regarding standard_conforming_strings in postgres

Changes regarding standard_conforming_strings in postgres

I found that my database recently started generating extra backslashes
on round-trips to the database.

The reason seems to be a change to standards_conforming_strings variable in postgresl
Beginning in PostgreSQL 9.1, the default is on (prior releases defaulted to off)

https://stackoverflow.com/a/3049139

 * I created a new protocol function (database-escape-backslashes database)
 * I changed the the generic mysql and postgres databases to return T
 * I made the postgresql-socket3 backend check for standards_conforming_string
   which is exposed in the underlying cl-postgres connection
 * It seems likely that postgresql-socket3 could always return NIL, as
   cl-postgres would probably handle this escaping anyway

This replaced some special case code in (database-output-sql (string
database))