Several history enhancements for new scrolling.

Implemented counting of wraparounds to implement new function
"validate_outputhistory", replaces "has_wrapped".

The "validate_outputhistory" function return true if the history object
in question is still valid, false if not.

Added "rewound_paragraph_was_newline_terminated" flag so it's possible
to tell whether the last paragraph in the output has been newline-
terminated or not.

Did some code-cleanup.