C++: fixed completion in braceless statements following a control statement.

- Changed generator to generate:
- Changed AST::lastToken to return 1 if there is none
- Changed Bind.cpp to set the scope of the block following a control
  statement to extend upto (and not including) the first token after
  the block. So basically, including any whitespace after the control
  statement.

Reviewed-by: Roberto Raggi