pgsql: Use portal pinning in PL/Perl and PL/Python

Use portal pinning in PL/Perl and PL/Python

PL/pgSQL "pins" internally generated portals so that user code cannot
close them by guessing their names. Add this functionality to PL/Perl
and PL/Python as well, preventing users from manually closing cursors
created by spi_query and plpy.cursor, respectively. (PL/Tcl does not
currently offer any cursor functionality.)

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/70d6226e4fba26765877fc3c2ec6c468d3ff4084

Modified Files
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src/pl/plperl/plperl.c | 8 ++++++++
src/pl/plpython/plpy_cursorobject.c | 8 ++++++++
2 files changed, 16 insertions(+)