Add another round-trip verification. For both original and generated
state, generate a diff from an initial, empty state. Verify that
these two diffs are the same.
The problem was that the round-trip verification code copies the
current state, which may contain intermediate Parser state for
multibyte characters and ANSI escape sequences. It then applies diffs
to that copy, which may appear as badly formed input.
Also removes some dead, never-used code.
* Fix inefficient STL use around Parser::UTF8Parser.
* Reduce typeid() usage, change some of it to a virtual method
* Do multiple-line scrolls as a single move
John Hood