pgsql: TG_table_name and TG_table_schema for pl/tcl, plus regression

Log Message:
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TG_table_name and TG_table_schema for pl/tcl, plus regression test and docs.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        pltcl.sgml (r2.39 -> r2.40)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pltcl.sgml.diff?r1=2.39&r2=2.40)
    pgsql/src/pl/tcl:
        pltcl.c (r1.102 -> r1.103)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/tcl/pltcl.c.diff?r1=1.102&r2=1.103)
    pgsql/src/pl/tcl/expected:
        pltcl_queries.out (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/tcl/expected/pltcl_queries.out.diff?r1=1.1&r2=1.2)
        pltcl_setup.out (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/tcl/expected/pltcl_setup.out.diff?r1=1.4&r2=1.5)
    pgsql/src/pl/tcl/sql:
        pltcl_queries.sql (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/tcl/sql/pltcl_queries.sql.diff?r1=1.1&r2=1.2)
        pltcl_setup.sql (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/tcl/sql/pltcl_setup.sql.diff?r1=1.3&r2=1.4)