minirst: combine list parsing in one function Bullet, option, field, and definition lists were parsed very similar code. They are now parsed by a single function (splitparagraphs). Some logic from the old parsing functions has been moved down to formatblock. This simplifies the parsing while putting the logic where it's really needed.

test-minirst: don't test on invalid reST input Input such as Only the left-most line (this line!) is significant for the indentation is not valid reStructuredText: the first line starts a block quote, but then the second line is not allowed to be unindented.