7.0.0: Extended match statement, cleanup & performance

• Fixed multiple semicolons yielding syntax errors, skip them instead
  (@thekid)
• Removed support for using curly braces as offset (e.g. $value{0})
  (@thekid)
• Merged PR #22: Stream tokens directly instead of using if/else cascade
  (@thekid)
• Merged PR #18: Allow match without expression: match { ... }. See
  https://wiki.php.net/rfc/match_expression_v2#allow_dropping_true
  (@thekid)
• Merged PR #17: Refactor parsing to allow blocks anywhere an expression
  is allowed. This not only allows fn() => { ... } but also using blocks
  in match expressions.
  (@thekid)
• Merged PR #21: Remove legacy XP annotations (#[@annotation]) - @thekid
• Merged PR #19: Remove support for Hack language annotations - @thekid
• Merged PR #20: Remove transformations API - @thekid