10/10 commits reworking the lexer This and the previous nine changesets completely revise the way significant whitespace is handled inside matrix and cell lists. Now instead of indefinite look ahead, we keep track of all tokens read and look back to previous tokens and ahead at most one character. If the surrounding context changes the parse, we unput the text for the current token and alter the start state, unput an additional character (typically a comma or semicolon) or both. Comments are now handled by a separate set of exlusive start states and there is no explicit handling of comments within any other patterns.