Use proper var names in emit() debug output
lex.go: Fix l.start = l.index in emit()

It was l.start += l.index which produced improper startPositions when the token
start position is greater than 1.
parse.go: Increase t.token length to 9!

I needed four back tokens to implement test OverlineBad0400. The tests have no
been updated for the increased tokens and that will come later.
parse.go: Add peekBackTo()

The tests have not been written yet, but are scheduled.
Add section test OverlineBad0400

Tests for indented section with two character adornment lines.