pgsql: Currently, nonfatal warnings are not trapped (as they should be)

Log Message:
-----------
Currently, nonfatal warnings are not trapped (as they should be) by
plperl - the attached small patch remedies that omission, and adds a
small regression test for error and warning output - the new regression
input and expected output are in separate attached files.

Andrew Dunstan

Modified Files:
--------------
    pgsql/src/pl/plperl:
        GNUmakefile (r1.23 -> r1.24)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/GNUmakefile.diff?r1=1.23&r2=1.24)
        plperl.c (r1.80 -> r1.81)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/plperl.c.diff?r1=1.80&r2=1.81)

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

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

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