pgsql: Refactor CREATE/ALTER DATABASE syntax so options need not be key

Refactor CREATE/ALTER DATABASE syntax so options need not be keywords.

Most of the existing option names are keywords anyway, but we can get rid
of LC_COLLATE and LC_CTYPE as keywords known to the lexer/grammar. This
immediately reduces the size of the grammar tables by about 8KB, and will
save more when we add additional CREATE/ALTER DATABASE options in future.

A side effect of the implementation is that the CONNECTION LIMIT option
can now also be spelled CONNECTION_LIMIT. We choose not to document this,
however.

Vik Fearing, based on a suggestion by me; reviewed by Pavel Stehule

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/15c82efd6994affd1d5654d13bc8911a9faff659

Modified Files
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src/backend/commands/dbcommands.c | 54 +++++++++-------
src/backend/parser/gram.y | 123 ++++++++++++++-----------------------
src/include/parser/kwlist.h | 2 -
3 files changed, 76 insertions(+), 103 deletions(-)