Special case parsing errors

[andymcn]

Like most parsers we suffer from the problem that parsing errors are pretty much limited to "syntax error". To reduce this problem we should identify common mistakes, slacken the BNF to allow the errors through the parser and then specifically check for those errors.

Split the sugar phase in 2, first the correctness storage, then the sugar phase.

[andymcn]

Done. The parse fix pass is now in place. Use it.