pgsql: Fix Unicode support in PL/Python Check calls of

Log Message:
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Fix Unicode support in PL/Python

Check calls of PyUnicode_AsEncodedString() for NULL return, probably
because the encoding name is not known. Add special treatment for
SQL_ASCII, which Python definitely does not know.

Since using SQL_ASCII produces errors in the regression tests when
non-ASCII characters are involved, we have to put back various regression
test result variants.

Modified Files:
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pgsql/src/pl/plpython:
plpython.c (r1.129 -> r1.130)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/plpython.c?r1=1.129&r2=1.130)
pgsql/src/pl/plpython/expected:
README (r1.2 -> r1.3)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/expected/README?r1=1.2&r2=1.3)

Added Files:
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pgsql/src/pl/plpython/expected:
plpython_unicode_2.out (r1.4)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/expected/plpython_unicode_2.out?rev=1.4&content-type=text/x-cvsweb-markup)
plpython_unicode_3.out (r1.4)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/expected/plpython_unicode_3.out?rev=1.4&content-type=text/x-cvsweb-markup)
plpython_unicode_5.out (r1.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/expected/plpython_unicode_5.out?rev=1.1&content-type=text/x-cvsweb-markup)