change joins so natural is represented by separate field to on/using
some fixes and tweaks to the reserved keyword handling, especially in
  the typename parser
get rid of the string overloads in the tests
change collate and in chartype to be a list of names
rearrange and add notes to the parser
rearrange part of the parser file
rename some functions in parser
more docs in Parser.lhs
add filter and within group aggregates
work around for haddock refusal to parse literal comment lines with *
  in first character position
get rid of code_units since these are not in sql2011
implement next value for
parse the nullary functions with reserved names
updates to the sql2003 file