pgsql: Support domains over composite types in PL/Perl.

Support domains over composite types in PL/Perl.

In passing, don't insist on rsi->expectedDesc being set unless we
actually need it; this allows succeeding in a couple of cases where
PL/Perl functions returning setof composite would have failed before,
and makes the error message more apropos in other cases.

Discussion: https://postgr.es/m/4206.1499798337@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/60651e4cddbb77e8f1a0c7fc0be6a7e7bf626fe0

Modified Files
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src/pl/plperl/expected/plperl.out | 88 ++++++++++++++++++++++++++--
src/pl/plperl/expected/plperl_util.out | 11 +++-
src/pl/plperl/plperl.c | 103 ++++++++++++++++++++++-----------
src/pl/plperl/sql/plperl.sql | 49 ++++++++++++++++
src/pl/plperl/sql/plperl_util.sql | 9 +++
5 files changed, 222 insertions(+), 38 deletions(-)