Ticket: #42

The comment syntax according to the report is:

  comment  -> dashes [ any<symbol> {any} ] newline

  symbol -> ascSymbol | uniSymbol<special|_|:|"|'>
  ascSymbol -> ... does not include : ...

This unfortunately forces sequences beginning '--:' to be comments, which appears to be unintentional.

Fix:

  comment -> dashes [ any<symbol|:> {any} ] newline