Simplified .dot codegen:

Simplified .dot codegen:

- draw a single arrow for all transitions between two given states
- label all arrows with corresponding character ranges in square
  brackests (no "default" label, single characters also appear in
  square brackets)
- .dot output became much smaller, thus pictures are drawn faster
  and generally look better: e.g. it takes ~10x less time to draw
  PHP lexer and the resulting graph is shaped better.