pgsql: Add support for anonymous code blocks (DO blocks) to PL/Perl.

Log Message:
-----------
Add support for anonymous code blocks (DO blocks) to PL/Perl.

Joshua Tolley, reviewed by Brendan Jurd and Tim Bunce

Modified Files:
--------------
    pgsql/doc/src/sgml:
        plperl.sgml (r2.70 -> r2.71)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plperl.sgml?r1=2.70&r2=2.71)
    pgsql/src/include/catalog:
        catversion.h (r1.552 -> r1.553)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.552&r2=1.553)
        pg_pltemplate.h (r1.8 -> r1.9)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_pltemplate.h?r1=1.8&r2=1.9)
    pgsql/src/pl/plperl/expected:
        plperl.out (r1.16 -> r1.17)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/expected/plperl.out?r1=1.16&r2=1.17)
    pgsql/src/pl/plperl:
        plperl.c (r1.153 -> r1.154)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/plperl.c?r1=1.153&r2=1.154)
    pgsql/src/pl/plperl/sql:
        plperl.sql (r1.13 -> r1.14)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/sql/plperl.sql?r1=1.13&r2=1.14)