pgsql: Fix plpython so that it again honors typmod while assigning to t

Fix plpython so that it again honors typmod while assigning to tuple fields.

This was broken in 9.0 while improving plpython's conversion behavior for
bytea and boolean. Per bug report from maizi.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=09130e5867d49c72ef0f11bef30c5385d83bf194

Modified Files
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src/pl/plpython/expected/plpython_trigger.out | 26 ++++++++++
src/pl/plpython/plpython.c | 62 +++++++++++--------------
src/pl/plpython/sql/plpython_trigger.sql | 23 +++++++++
3 files changed, 76 insertions(+), 35 deletions(-)