pgsql: Backpatch: Fix tsvector_out() and tsquery_out() to escape

Log Message:
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Backpatch: Fix tsvector_out() and tsquery_out() to escape backslesh, add test of that.
Patch by Bruce Momjian <bruce@momjian.us>

Tags:
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REL8_2_STABLE

Modified Files:
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    pgsql/contrib/tsearch2:
        query.c (r1.29.2.1 -> r1.29.2.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/query.c?r1=1.29.2.1&r2=1.29.2.2)
        tsvector.c (r1.26.2.1 -> r1.26.2.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/tsvector.c?r1=1.26.2.1&r2=1.26.2.2)
    pgsql/contrib/tsearch2/expected:
        tsearch2.out (r1.24 -> r1.24.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/expected/tsearch2.out?r1=1.24&r2=1.24.2.1)
    pgsql/contrib/tsearch2/sql:
        tsearch2.sql (r1.13 -> r1.13.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/sql/tsearch2.sql?r1=1.13&r2=1.13.2.1)