SQL99 feature list

I've just updated features.sgml to have a list of supported features
followed by a list of unsupported ones. There are some items in the
"unsupported list" which look easy to do. I've got patches for a "MATCH
SIMPLE" clause on referential integrity declarations, and am developing
patches for CREATE CAST, DROP CAST, and probably a few more items which
could be simple parser additions or changes. Look at

http://developer.postgresql.org/docs/postgres/features.html

for the most recent version (it is not there yet but I'd expect it to be
there soon).

I'd like to look at supporting the various shorthand literal notations
like B'0101', X'ABCD', and N'national' in a better way in the lexer to
make sure that the information gets to the parser more robustly. Right
now, N'national' is not supported at all and the other two forms are
supported by transforming the input locally in the lexer which seems to
work but does not extend to the NATIONAL CHARACTER case. Comments and
suggestions are welcome.

Y'all may want to look at features.sgml to find projects if you are
looking for something to do; there are several items which look to be
relatively easy to accomplish and others at various levels of
difficulty...

- Thomas