pgsql: Add regression tests for previously-untested PL/Perl features.

Log Message:
-----------
Add regression tests for previously-untested PL/Perl features. From
Andrew Dunstan.

Modified Files:
--------------
    pgsql/src/pl/plperl:
        GNUmakefile (r1.20 -> r1.21)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/GNUmakefile.diff?r1=1.20&r2=1.21)

Added Files:
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    pgsql/src/pl/plperl/expected:
        plperl_shared.out (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/expected/plperl_shared.out?rev=1.1&content-type=text/x-cvsweb-markup)
        plperl_trigger.out (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/expected/plperl_trigger.out?rev=1.1&content-type=text/x-cvsweb-markup)
    pgsql/src/pl/plperl/sql:
        plperl_shared.sql (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/sql/plperl_shared.sql?rev=1.1&content-type=text/x-cvsweb-markup)
        plperl_trigger.sql (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/sql/plperl_trigger.sql?rev=1.1&content-type=text/x-cvsweb-markup)