pgsql: Add regression tests for CSV and \., and add automatic quoting of

Log Message:
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Add regression tests for CSV and \., and add automatic quoting of a
single column dump that has a \. value, so the load works properly.  I
also added documentation describing this issue.

Backpatch to 8.1.X.

Tags:
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REL8_1_STABLE

Modified Files:
--------------
    pgsql/doc/src/sgml/ref:
        copy.sgml (r1.70 -> r1.70.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/copy.sgml.diff?r1=1.70&r2=1.70.2.1)
    pgsql/src/backend/commands:
        copy.c (r1.254.2.2 -> r1.254.2.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/copy.c.diff?r1=1.254.2.2&r2=1.254.2.3)
    pgsql/src/test/regress/expected:
        copy2.out (r1.22 -> r1.22.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/copy2.out.diff?r1=1.22&r2=1.22.2.1)
    pgsql/src/test/regress/sql:
        copy2.sql (r1.13 -> r1.13.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/copy2.sql.diff?r1=1.13&r2=1.13.2.1)