Refactor generate source

[User4martin]

See comments on #295

[User4martin]

See also #288

• Move old style include into scanline

• Move checking for missing close tag into scanline

• In Scanline break the case into groups.
  first group all cases that start with <
  2nd group all cases that end in >
  putting each group into an if gives some extra speed.
  (isHandled is needed for the 3rd group, not matched by any before)

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The isHandled will be removed in one of the later pull requests. As the entire switch structure will be changed.

[RyanZim]

Thanks for doing this; will try to review this when I get a chance; please ping me if anything is waiting my attention for more than 7 days.

[RyanZim]

As is probably obvious, I haven't gotten around to reviewing this for a long while, and with my work schedule, it's unlikely I can make this a priority anytime soon. I'll leave this for the other maintainers.