pgsql: Add dynamic record inspection to PL/PgSQL, useful for generic

Log Message:
-----------
Add dynamic record inspection to PL/PgSQL, useful for generic triggers:

tval2 := r.(cname);

or

columns := r.(*);

Titus von Boxberg

Modified Files:
--------------
pgsql/doc/src/sgml:
plpgsql.sgml (r1.92 -> r1.93)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpgsql.sgml.diff?r1=1.92&r2=1.93)
pgsql/src/pl/plpgsql/src:
pl_comp.c (r1.104 -> r1.105)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_comp.c.diff?r1=1.104&r2=1.105)
pl_exec.c (r1.167 -> r1.168)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_exec.c.diff?r1=1.167&r2=1.168)
pl_funcs.c (r1.50 -> r1.51)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_funcs.c.diff?r1=1.50&r2=1.51)
plpgsql.h (r1.72 -> r1.73)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/plpgsql.h.diff?r1=1.72&r2=1.73)
scan.l (r1.47 -> r1.48)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/scan.l.diff?r1=1.47&r2=1.48)
pgsql/src/test/regress/expected:
plpgsql.out (r1.47 -> r1.48)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/plpgsql.out.diff?r1=1.47&r2=1.48)
pgsql/src/test/regress/sql:
plpgsql.sql (r1.40 -> r1.41)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/plpgsql.sql.diff?r1=1.40&r2=1.41)