pgsql: Python 2.2 is no longer supported

Python 2.2 is no longer supported

It was already on its last legs, and it turns out that it was
accidentally broken in commit 89e850e6fda9e4e441712012abe971fe938d595a
and no one cared.  So remove the rest the support for it and update
the documentation to indicate that Python 2.3 is now required.

Branch
------
master

Details
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http://git.postgresql.org/pg/commitdiff/1d158d7f9841d7993f7b5990f311e3595db7960b

Modified Files
--------------
doc/src/sgml/installation.sgml  |    2 +-
src/pl/plpython/expected/README |    3 ---
src/pl/plpython/plpython.h      |    7 -------
3 files changed, 1 insertions(+), 11 deletions(-)