pgsql: In PL/Tcl tests, don't choke if optional error fields are missin

In PL/Tcl tests, don't choke if optional error fields are missing.

This fixes a portability issue introduced by commit 961bed020: with a
compiler that doesn't support PG_FUNCNAME_MACRO, the "funcname" field of
errorCode won't be provided, leading to a failure of the unset command.
I added -nocomplain to the unset commands for filename and lineno too, just
in case, though I know of no platform that wouldn't populate those fields.
(BTW, -nocomplain is new in Tcl 8.4, but fortunately we dropped support
for pre-8.4 Tcl some time ago.)

Per buildfarm member pademelon.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/5b29e6b688d1e783a098aa24f9e795f8de798a87

Modified Files
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src/pl/tcl/expected/pltcl_setup.out | 6 +++---
src/pl/tcl/sql/pltcl_setup.sql | 6 +++---
2 files changed, 6 insertions(+), 6 deletions(-)