Remove obsolete information schema tables

I propose this patch to remove the information schema tables
SQL_LANGUAGES, which was eliminated in SQL:2008, and SQL_PACKAGES, which
was eliminated in SQL:2011. Since they were dropped by the SQL
standard, the information in them was no longer updated and therefore no
longer useful.

This also removes the feature-package association information in
sql_feature_packages.txt, but for the time begin we are keeping the
information which features are in the Core package (that is, mandatory
SQL features). Maybe at some point someone wants to invent a way to
store that that does not involve using the "package" mechanism
anymore.

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Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services