plpsm - plpgpsm: sqlstate variable support.

Log Message:
-----------
sqlstate variable support.

This functionality is compatible with DB2. If you define variable sqlstate,
then system fill this variable or reset this variable over exception
or warning handler.

Modified Files:
--------------
    plpgpsm/src:
        gram.y (r1.11 -> r1.12)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plpsm/plpgpsm/src/gram.y.diff?r1=1.11&r2=1.12)
        pl_comp.c (r1.4 -> r1.5)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plpsm/plpgpsm/src/pl_comp.c.diff?r1=1.4&r2=1.5)
        pl_exec.c (r1.11 -> r1.12)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plpsm/plpgpsm/src/pl_exec.c.diff?r1=1.11&r2=1.12)
        plpgpsm.h (r1.11 -> r1.12)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plpsm/plpgpsm/src/plpgpsm.h.diff?r1=1.11&r2=1.12)