Fluent Syntax Spec 0.4.0

• Added the Placeable production as a wrapper for expressions in patterns.

  This allows storing more precise information about the whitespace around the placeable's braces.

• Separated the expr type into inline_expr and block_expr.

  This mirrors the EBNF, where a select expression cannot by an argument to a call expression nor selector of another select expression without being wrapped in braces.

• The dash - is not allowed at the beginning of identifiers.

  There's an ongoing discussion in #62 about using the leading - for private messages in the future.

• The question mark ? is not allowed in identifiers.

  We want to start with a more strict syntax for identifiers. See the discussion in #65.

• Small EBNF fixes:

  • Allowed multiline comments.
  • Allowed inline space in blank lines between entries.